Potential buyer

Lots of questions I suppose. Long story short, I’m having a second kid and losing my desktop space. Hell I’m losing the whole room, chair,desk, my lovely 48 inch curved monitor, you know how life changes. Recently my friend group has been itching to get back into WoW. I saw threads here talking about specific add ons and a kind of consensus that WoW on a portable is fine except mythics and raids, at least in controller mode.

First question: are these devices just equipped for usb peripherals? Like on a raid night my existing mnkb can just plug in? Or is there something or proprietary?

It’s been a few years since I’ve played wow, is it easy to switch back and forth with addons and the like for controller to MnK?

What version of this device should I get? I really only plan to play Helldivers, WoW, and maybe rust. My competitive shooters and the like I’m good with just my Xbox.

I’ve heard certain versions use a steam OS? I’d prefer something like windows and use steam separately. Is this similar to switching partitions?

Thanks for your help.