You might follow the link in my signature to get some thoughts on room. You only have four pullets and they are all the same age so a lot of that stuff won’t apply but you might pick up some ideas. That article is more to help you think and understand, not to tell you exactly what to do. One thing I’ll mention is that chickens do not understand the concept of space in the coop versus space in the run. What they understand is space wherever it might be. How much space you need in the coop or in the run or all together will depend a lot on your management techniques and other factors. We are all unique in our climate, flock make-up, goals, and many other factors so there is not any one specific square feet per chicken that suits us all. For only four hens as you describe your set-up sounds pretty good, but that will depend some on your climate. How available is that outside area year around?
We use a tremendous number of different things we use as nests. You can make them as simple or as complicated as you desire, all the way from roll-out nest boxes to just setting a cardboard box in the corner and fill it with some type of nesting material. For nesting material some people use hay, straw, pine shavings, pieces of carpet or rags, shredded paper (not newspaper as the ink stains everything black), one lady even uses Spanish moss. People tend to care about this much more than the chickens do. I use long grass I cut and dry from where I don’t mow. It’s free for just a little labor. I like free.
As they said, chickens poop a lot when they sleep. And they tend to sleep on the highest thing available. When you lay out your coop and run, you need to position your nests, feeders, and waterers where they don’t poop in them at night. You can do that by separation. I built in a brooder to my coop I raise so many chicks out there. That brooder is under the main roosts so the top acts as a droppings board. I have another separate roost for juveniles over my nests. Again the top is a droppings board. I collect that pure poop by raking it into a bin as required and use that in my compost bin. Poop management is often a major part of managing chickens, especially in smaller spaces. We all have our unique ways to manage that.
It sounds like you have settled on nipples. I don’t use those but a lot of people do and are very happy with them. I suggest you start a new thread with a title of something like, “How do I keep nipples from freezing”. Being specific in your title will help attract the people you want to attract. You can search on here if you want and should be able to find something, there are a lot of threads on that, but with your own thread you can direct it where you want it to go. Besides if people only asked questions that have never been asked this forum would soon dry up. It’s still worth while searching so you better know what questions to ask.
However you water them it is very important to keep their water clean. The nipples help with that but your water storage area also has to keep trash and poop out. If mosquitoes can get to the water they will breed in there. Dirty or poopy water is a source for diseases.
One trick to keep the chickens from perching on top of waterers or feeders is to hang something over them so the chickens can’t get up there. A popular way is to hang an empty plastic jug like a gallon milk jug filled with sand to keep the wind form blowing it around. I cut some plywood and hung it in a way that a chicken will flip off if it flies up there.
Don’t worry about giving too much information in your posts. If you are too brief it just sparks questions or we aren’t sure how to answer.
It sounds like you are off to a good start. Welcome to the adventure.