As a nurse, I can tell you that it's table saws that typically take off fingers. I'll use one but refuse to push anything through by hand, don't care how big it is. My son makes me nervous doing it with his hands, but I admit he handles tools well. Circular saws are easy. I learned on one that had a broken blade guard so learned not to depend on it. Have never hurt myself on one and have used one for years. Yes, female here. We've been through some nail guns here. IMO unless you are building a house it's a waste of money; you do save time by shooting them, but not really that much, for something like a coop. You'll have a drill, anyway, and often can just use a screw. Screws come out a LOT easier if you change your mind, too.
I'd save the smallest one, in the first pic, for a broody pen/isolation pen. It will come in VERY handy.
The store bought coop, IMO, has an awfully small run, even for just one chicken. I'd anchor it mostly by adding on a much larger area, sinking fence posts (or 4x4's or whatever) at the corners.