From your other thread, I believe you are talking about supplemental light to get them to lay this winter, not regular light from windows, though I am not sure. If you want to provide the extra light for winter laying, all you need is enough light so you can read a newspaper in there at night. It does not take a bright light. I think they are a little calmer if the light is not too bright anyway. Putting a small wattage bulb on a timer is a great way to go about this.
I don't provide supplemental light, but let mine have the downtime to recharge their system. After a long time of laying without the break they get from a molt, the egg shells can get lighter colored and they can reduce the frequency of laying. But I don't generally have pullets coming into lay around Christmas like you do.
As far as windows, I just have one. It's on the north side since that is the only outside wall I built for my coop. All I was after was enough light so I can see when I am in there working. I did put in a single incandescent light for when I go in there at night to count them or work in there. That comes in real handy. A couple of outlets is a real good idea too for a walk-in coop, but that's necessary for one the size of yours. With your coop, just a regular nightlight may be enough to extend the laying, or maybe get yours started, plus allow you to see in there at night.
