https://www.mcmurrayhatchery.com/chickcare.html
https://www.cacklehatchery.com/chick-care-instructions/
For the first two days, yes. It's probably better if they cannot get more than 3 feet away from the heat source in their first two days.
After that, too much space is not an issue.
Too little space causes problems.
Figure 2 square feet per chick at 8 weeks old.
Figure 1/2 square foot per chick for the first two weeks.
In between, they need in-between amounts. (But if you just start with 2 square feet per chick, you don't have to bother changing the size later.)
Option 1, start with something big enough, and maybe partition it for the first few days, after that let them have access to all the space for the rest of their growing time.
Option 2, start them in one space (plastic storage tub or cardboard box are common), later realize they've outgrown it, so provide more space (bigger storage tub, tape more cardboard boxes to the first one, go build something out of plywood, or just move them to the coop.)
It sounds like you would rather NOT try option 2
Need, no. Like, yes. Anytime you feel like adding them. If you put in something really low (like a piece of wood a few inches high), they will climb on and off it before they are even a week old. They usually play on it in the daytime and sleep on the floor under the heat source until they're a bit bigger, but some will sleep on a roost by the time they're 2-3 weeks old: it depends on the individual chicks and on the temperature.
Yes, but it's a good idea to put a layer of paper towel over the shavings for the first day or two, so the chicks learn more quickly which stuff is food. After that, they can have access to the shavings.
They will nibble some of the shavings, and they will scratch in the shavings and eat little bits of something (broken shavings? spilled food? little bugs? I don't know.) But that will not hurt them.
The upper edge of the feeder or waterer should be no higher than the back of the smallest chick. At first, that means it needs to sit on the floor.
Chick feeders and waterers are usually designed to just sit on the floor and not hang, because by the time the chicks are big enough to reach a higher one--they may be eating so much food they need a bigger one anyway.
Yes, they will scratch shavings into the feed and water.
Various solutions exist. I usually just clean it out lots of times for the first few days, then put in a few bricks to make a raised platform. (Just several bricks laying next to each other.) The feed and water go on the platform, and the chicks can hop up onto the platform to eat. Because it's up, even if they scratch shavings onto it, they tend to scratch them back off again too
Heat lamps:
--better for large numbers of chicks
--cheaper to buy
--heats the entire area (good in cold weather, bad in hot weather)
--attracts chicks to it, because it gives off light
--can cause a fire if it gets knocked down or is too close to something that can burn.
Heat plates:
--much less likely to cause a fire
--does not heat the entire area (great in hot or warm weather)
--chicks often grow feathers faster (because it doesn't heat the entire area)
--chicks are thought to sleep better when the nights are dark, and definitely do less picking at each other
--chicks can get lost and need help to get back to the heat (because it does not give off light, and because it doesn't warm the area around it as much, so they don't recognize where to go to get warm.)
--chicks have to come out from under the heat to eat and drink, which can be a problem in the first hours if they are both cold and hungry/thirsty
--more expensive
I've always used heat lamps and have never had a fire, but fires caused by heat lamps definitely do happen. By "fire," I mean it burns down the entire chicken house (happened to someone I know), or it catches the shed/barn/house on fire. Tends to kill chickens and sometimes people.
In your case, I suspect a heat plate would be a better choice. But you might want a heatlamp too for the very first day, to be sure they all get warm and eat and drink after shipping. Then remove the heat lamp that evening, be sure they are sleeping under the heat plate, and check frequently during the second and third days. Tuck any peeping, distressed chicks back under the heat plate, and be sure they're in the right place after dark.
If you do use a heat lamp, be sure the space is large enough for the chicks to get away from the heat. I think it's best if they can go somewhere as cool as 70 degrees anytime after the first day or two. Access to colder-yet temperatures is fine, too, as long as they have a suitable warm spot (under the heatlamp or heat plate.)
First day: warmth, feed, water
Second day: as above, also talk to them and look at them. Check for poopy butts. (Check butts every day in the first week; if they're fine at one week, they will probably stay fine.)
Third day: remove paper towel from brooder, and they will start to learn about wood shavings. Put in a dish of grit.
You can also offer a bit of wet chicken food, in a small dish (like the lid from a jar) or on your finger. They usually like it. It's a good treat to make them like you, and still contains all the right nutrients for them to grow.
Fourth day and following:
Can give them a clump of sod or a shovelful of dirt to dig through.
If the weather is warm, can take them outside on the lawn briefly.
Can offer grass, either attached to sod (so they can bite off little bits) or cut into tiny pieces (similar in size to the chick food they have.)
Can put in things for them to climb on and run around.
What chickens really like to do is eat, dustbathe, sit on things, practice flying, and forage for food.
So the best enrichment is to allow for those things.
I like to provide bedding they can "forage" in--dry leaves, small amounts of hay, a scoop of compost or dirt, etc (depends on what I have available.) I try to just add a little pile of something (bedding/forage) every day or so. They may be scared of the new thing, but pretty soon they're looking at it, climbing on it, scratching it around, looking for munchies in it.
It is best if they eat mostly chick starter, but a certain amount of greens seems to cause no harm. And when they busily scratch through the bedding and eat a small nibble here and there, they don't seem to eat large amounts--they still keep going back to the feeder to fill their crops.
https://www.cacklehatchery.com/chick-care-instructions/
Is there such a thing as too much space in a brooder?
For the first two days, yes. It's probably better if they cannot get more than 3 feet away from the heat source in their first two days.
After that, too much space is not an issue.
Too little space causes problems.
How much space does a 6 week old chicken need?
Figure 2 square feet per chick at 8 weeks old.
Figure 1/2 square foot per chick for the first two weeks.
In between, they need in-between amounts. (But if you just start with 2 square feet per chick, you don't have to bother changing the size later.)
I"m wondering how brooder sizing works? Do you have something big enough for them their entire time as chicks, and wall off part until they grow bigger?
Option 1, start with something big enough, and maybe partition it for the first few days, after that let them have access to all the space for the rest of their growing time.
Option 2, start them in one space (plastic storage tub or cardboard box are common), later realize they've outgrown it, so provide more space (bigger storage tub, tape more cardboard boxes to the first one, go build something out of plywood, or just move them to the coop.)
It sounds like you would rather NOT try option 2

Do chicks need roosts in the brooder? starting at what age?
Need, no. Like, yes. Anytime you feel like adding them. If you put in something really low (like a piece of wood a few inches high), they will climb on and off it before they are even a week old. They usually play on it in the daytime and sleep on the floor under the heat source until they're a bit bigger, but some will sleep on a roost by the time they're 2-3 weeks old: it depends on the individual chicks and on the temperature.
Can you use shavings for bedding?
Yes, but it's a good idea to put a layer of paper towel over the shavings for the first day or two, so the chicks learn more quickly which stuff is food. After that, they can have access to the shavings.
They will nibble some of the shavings, and they will scratch in the shavings and eat little bits of something (broken shavings? spilled food? little bugs? I don't know.) But that will not hurt them.
Is it better to have a hanging feeder and waterer?
The upper edge of the feeder or waterer should be no higher than the back of the smallest chick. At first, that means it needs to sit on the floor.
Chick feeders and waterers are usually designed to just sit on the floor and not hang, because by the time the chicks are big enough to reach a higher one--they may be eating so much food they need a bigger one anyway.
Yes, they will scratch shavings into the feed and water.
Various solutions exist. I usually just clean it out lots of times for the first few days, then put in a few bricks to make a raised platform. (Just several bricks laying next to each other.) The feed and water go on the platform, and the chicks can hop up onto the platform to eat. Because it's up, even if they scratch shavings onto it, they tend to scratch them back off again too

Are heating plates or heat lamps better?
Heat lamps:
--better for large numbers of chicks
--cheaper to buy
--heats the entire area (good in cold weather, bad in hot weather)
--attracts chicks to it, because it gives off light
--can cause a fire if it gets knocked down or is too close to something that can burn.
Heat plates:
--much less likely to cause a fire
--does not heat the entire area (great in hot or warm weather)
--chicks often grow feathers faster (because it doesn't heat the entire area)
--chicks are thought to sleep better when the nights are dark, and definitely do less picking at each other
--chicks can get lost and need help to get back to the heat (because it does not give off light, and because it doesn't warm the area around it as much, so they don't recognize where to go to get warm.)
--chicks have to come out from under the heat to eat and drink, which can be a problem in the first hours if they are both cold and hungry/thirsty
--more expensive
I've always used heat lamps and have never had a fire, but fires caused by heat lamps definitely do happen. By "fire," I mean it burns down the entire chicken house (happened to someone I know), or it catches the shed/barn/house on fire. Tends to kill chickens and sometimes people.
In your case, I suspect a heat plate would be a better choice. But you might want a heatlamp too for the very first day, to be sure they all get warm and eat and drink after shipping. Then remove the heat lamp that evening, be sure they are sleeping under the heat plate, and check frequently during the second and third days. Tuck any peeping, distressed chicks back under the heat plate, and be sure they're in the right place after dark.
If you do use a heat lamp, be sure the space is large enough for the chicks to get away from the heat. I think it's best if they can go somewhere as cool as 70 degrees anytime after the first day or two. Access to colder-yet temperatures is fine, too, as long as they have a suitable warm spot (under the heatlamp or heat plate.)
Is there any enrichment you can give chicks?
First day: warmth, feed, water
Second day: as above, also talk to them and look at them. Check for poopy butts. (Check butts every day in the first week; if they're fine at one week, they will probably stay fine.)
Third day: remove paper towel from brooder, and they will start to learn about wood shavings. Put in a dish of grit.
You can also offer a bit of wet chicken food, in a small dish (like the lid from a jar) or on your finger. They usually like it. It's a good treat to make them like you, and still contains all the right nutrients for them to grow.
Fourth day and following:
Can give them a clump of sod or a shovelful of dirt to dig through.
If the weather is warm, can take them outside on the lawn briefly.
Can offer grass, either attached to sod (so they can bite off little bits) or cut into tiny pieces (similar in size to the chick food they have.)
Can put in things for them to climb on and run around.
What chickens really like to do is eat, dustbathe, sit on things, practice flying, and forage for food.
So the best enrichment is to allow for those things.
I like to provide bedding they can "forage" in--dry leaves, small amounts of hay, a scoop of compost or dirt, etc (depends on what I have available.) I try to just add a little pile of something (bedding/forage) every day or so. They may be scared of the new thing, but pretty soon they're looking at it, climbing on it, scratching it around, looking for munchies in it.
It is best if they eat mostly chick starter, but a certain amount of greens seems to cause no harm. And when they busily scratch through the bedding and eat a small nibble here and there, they don't seem to eat large amounts--they still keep going back to the feeder to fill their crops.