I have a lcd 256gb and played a lot of games (little games and bigger stuff like rdr2) from my sd card, never had any big issues. I didn’t compare both directly but it never bothered me.
yeah the game need to be on steam but you can add it as a non-steam game and stream it that way, works fine.
If it’s not possible for some reason, there’s probably a way to do it on desktop mode with a linux app but never tried that.
In theory you can play anything, even install windows and use it like a regular pc. In practice it’s a linux machine and a very weird one on top of that. It works best and it’s fun to use when you stay on steam, everything else requires some effort (more or less depending on the game).
If it’s not possible for some reason, there’s probably a way to do it on desktop mode with a linux app but never tried that.