I'll be making plans for a coop next week so I'm getting as much info as I can now.

We have a horse stall in the barn that we were going to convert to sleeping quarters for the hens, but I think they might get bored in there if they had to spend too much time inside. Is it possible to teach the chickens to use two different coops? (one for good weather and one inside for bad weather?)
I doubt the chickens will use two different coops depending on weather, especially as much as the weather changes here ! you might be better off to build a coop well above the ground, well secured (sturdy door with a complicated latch, or a sliding door heavy enough that a coon could not raise it) or build your coop inside the barn, either with access to the outside run, or with a run inside the barn --- chickens don't get so bored if you give them something to play with, like a head of cabbage -- and let them out to free-range from the run(s)
we have 16" x 16" x 12' open troughs surrounding our run, nothing has climbed over them nor dug underneath, with 2x4 welded wire stapled to the inside, our only known predator attack was when DS left the run door (sliding glass with a latch) open .. possibly also when he and the dog were away for a weekend ... we did lose one hen when we could not get her into the run after free-ranging one day -- hubby lost count and didn't realize we were one short ...
run has a big silver tarp over it, both to discourage avian predators, and to provide shelter for the frequent precip ...
our hens normally free-range only when we are out in the yard with them -- we have redtails, golden and bald eagles, bobcats (who usually stay within the blackberry thickets), coons and opossoms, coyotes (who are bold, they run down the middle of the street in the middle of the day), and possibly cougars -- also feral dogs and feral cats ...
we built our original coop and run close to the house, so that predators would have to run across expanses of lawn to get to the coop .. our oaks shade the area but the only "predator hiding place" nearby is the Indian plum bush thicket surrounding the oak tree, and it's relatively open now, until it is fully leafed out
also, it's within the electronic fence that confines the dog -- she's a pretty good territorial bark machine! -- German shorthaired pointer -- we also have a part-Siamese ex-tomcat .. and their scent likely deters predators too