Follow the link in my signature to get some of my thoughts on that. Some of it won’t apply to your situation but some will. It does not give you hard and fast numbers and may not be a great help right now but in the future something you read may come in handy. It may help convince you to go bigger rather than smaller though. And it may help you decide how to manage them.
One thing that is going to help you get by with less space is that you are going to have an all-hen flock. No roosters and I doubt you will be having a broody hen hatch and raise chicks with the flock. But you say you will be integrating later, so your space requirements at that time go up. You may be able to deal with that using something temporary.
I don’t see you letting them out a bit every day being all that relevant to how much space you need. I encourage you to do that but there will be days you don’t do that. Life gets in the way of those types of plans.
I don’t know where you are located so I don’t know what extremes of hot or cold you may be looking at. It often helps with questions if you modify your profile to at least give us a clue which side of the equator you are on. Narrowing it down a little more can really help.
Chickens do not understand the concept of room in the coop versus room in the run. They just understand whether or not they have room somewhere when they need it. I don’t know how predator proof your run will be so you may or may not be locking them in the coop at night or give them access to the run all the time. I don’t know your weather so I don’t know if the run will be accessible year around.
This is not just about how much space your girls need. Your comfort and convenience are very important. You need to be able to access everything inside the coop. Being able to stand up in the run without banging your head or not having to work on your knees makes life so much more pleasant. I find the less I crowd them the fewer behavioral problems I have to deal with, the more flexibility I have to deal with those and other problems, and the less hard I have to work. This is mostly about you, not them.
It sounds like you are going to be building it yourself since you are looking at plans. I don’t fully trust you to stop at a total of 6 either, but since you are integrating a little extra room can come in handy. Since most building materials come in standard 4’ or 8’ lengths I suggest you look at plans for a 4’ x 8’ coop. 4’ x 6’ wouldn’t be bad but with the 8’ you won’t have a lot of cutting and waste. Look at your roof. I really like enough overhang so I can leave the tops of the walls open for ventilation (covered with hardware cloth for predators) without rain getting in. You need it to slope also so water runs off in the direction you want it to. You don’t want water running off into your run or your access door when gathering eggs and getting it even wetter and you don’t want a flat roof where water stands. It will rot your roof or leak through.
A 4’ x 8’ isn’t really big enough for you to get inside and work so make sure you have a few openings to access the inside. I’d look at elevating it and making it at least 4’ high. Getting a slope on your roof may cost you a bit more in building materials. If you are careful you can get enough stuff in 4’ to meet your vertical needs, especially if you hang your nests outside and keep them really low. You need height for any bedding, room for nest openings above that, your roosts need to be higher than your nests so they sleep in the roosts instead of in the nest, and the roosts need to be below your ventilation up high so a breeze doesn’t hit them if you live in a cold climate. If you live in a warm climate like the US Gulf Coast, cold weather worries go away.
I don’t know what your run will look like. If it’s just fence posts and wire you have a lot of flexibility, especially if you are not going to cover it. I suspect you will build something fairly substantial and pretty predator proof, including a roof or at least a wire cover. Remember that lumber often is pretty inexpensive in 8’ lengths. You can get a lot of different lengths and width of rolls of wire. For six hens I would not be happy with a 4’ x 8’ run. If you put a solid roof on it, a 6’ width would not a horrible. A 6’ x 8’ run for six hens would probably work. I’d want more but it should work. With it that small you may have to do more poop management, this is an example of working harder, but your space is limited and you are probably going to have to do something with poop management anyway. With chickens pooping in a smaller area you just may have to do that more frequently.
I understand your frustration. You don’t have the experience and you can get a lot of conflicting advice on here. And there are no magic numbers for any of this. My suggestion is to provide as much room as you reasonably can, whether that is coop, run, roosts, brooder, or even nests instead of going with the bare minimums. People don’t complain about having extra room.
Good luck!
