Hmm, I hadn't thought of using GIFs instead of screenshots - I worry about size/quality on that front, but I'll think about it! I have an animated thumbnail/cover image, which I'm told helps.
I sort platforms alphabetically, and if I didn't, I think I'd probably be happy to sacrifice some Windows users (edit: this is a tongue-in-cheek comment - no altars involved, promise!) in order to promote the platform I use :D
Regarding stream-friendliness of the UI, I haven't found any nice solutions on that front, but I have been working on some features that will likely be relevant to streamers as part of an upcoming patch.
Best of luck with your project.