-20F here isn't uncommon at all. Ventilation is more important than keeping heat in. With the sentinels, the only air flow comes through the main coop door unless you modify it
You have to kneel or move it to a clean spot and then clean up the mess. It does come with trays though for the coop you just take out and dump. Super nice if you don't put them too close together. I also don't stick with the whole 10/4/1 rule people insist on though. I go off the actual birds...
I will say the nice thing about the taller one is the roost in the run. My grey prefab has one too, and the birds like to use it especially after snow falls so they can get outside but not have to stand in the cold snow
If you're doing bantams, that would probably work. I have 3 of them. Definitely not perfect, but they're good enough if you keep an eye on them. Much more stable than the wooden ones