In Pennsylvania you will get some days in winter when they cannot go outside. The 4 square feet is kind of small for that but if you fix an area of your run so snow does not accumulate and it is protected from the wind you can get by. In my opinion a 4' x 8' coop wold be an absolute minimum. Most building materials come in 4' and 8' standard dimensions so if you use those you can often reduce cutting, fitting, and waste. Actually a 6' wide isn't too bad, you can use the 2' cut-offs for nests and such plus you can use regular 8' material for the roof so you get enough overhang to leave the top of the walls open for ventilation. If you build it tall enough so you can walk in, 6' wide gives you some room to move.
Let's look at that coop in your last link. 12' long, 5'-8" wide and 5'-6" high. That's the run section, the bit surrounded by wire. It's a bit tight for 8 hens but probably not horrible. If you ever try to integrate new chickens it would probably be horrible. It's not tall enough to stand up in which is a real bummer.
I did not see a dimension for the coop section, the part covered in wood that protects them from weather. My guess is 5'-8" x 4'. With three roosting bars where can you put the water and feed without them pooping in them from the roost? In good weather you can put the feed under the coop section and keep it dry but what will you do in a blizzard? They did not show how the inside is set up, a photo would really be helpful. I can't see 8 hens spending three or four days straight in there when a bad weather spell hits.
It has 6 nests. For 8 hens you need two, three at at the most. Ventilation is really inadequate. You need ventilation in winter as well as summer.
That coop is probably good for 5 hens if you add ventilation. You might be able to get 6 in there but if you overcrowd then you can get serious behavioral problems.
If I were in Pennsylvania and knew the most I would ever have was 8 hens, my ideal coop would be a 6' x 8' walk-in. The roof would be sloped so water did not run down in the run. The human door would be in the 6' side. I'd have overhang on both 8' long sides so the top 3-1/2" of the walls were permanently open but covered with hardware cloth to keep predators out. That overhang helps keep rain and snow out. 3'1/2" works out great with 2x4 rafters. I'd have one or two windows that can be opened for ventilation in summer, covered with hardware cloth to keep predators out. I'd have a storage closet for feed. It's not just about room for chickens, it is room for you too.
The run would be 8' wide to match the coop with the coop on the prevalent winter wind side to block that cold winter wind and make your run more usable. I'm having trouble with the length of the run. It kind of depends on how you build it and what material you use. If it is just fence posts and wire it's not going to be that expensive to make it a decent size. If you go with dimensioned lumber covered with hardware cloth the cost is going to go up pretty fast. You might get by with an 8' x 8' run with the coop, but i'd prefer more length.
Anyway, those are my thoughts. Good luck!