Been a while I looked at this (as in, before the Switch came out), but yeah, it's the same form for every kind of company, and if you're a sole trader you probably just can make up things and/or register under your own name instead of a company name, it's not very scary at all. Dunno if that part changed, though, but one sure thing though, Wii U support died as soon as the Switch came out. 3DS should still be a thing. And no, don't think you can submit homebrew formats, Nintendo really want their own format (something like packed CIA or something) with a ton of metadata that says exactly how your game is going to be distributed and isn't really compatible with homebrew loaders, I think. They want to make sure it works on a devkit before submitting your game to them.
Sony probably have a similar pipeline, so good luck.