Ah yea, for some reason I missed C, which is the only way to get out of the menu. X closes the game, so I thought I'd tried every key but I guess I missed C when closing it. I even made a point of trying Z for that very reason, but I guess I forgot to check C.
As expected though, controller definitely feels like the way to go. I have very little 3D platforming experience though, and I usually invert my X-axis camera controls in 3D games (not an option here), so it's been a STRUGGLE compared to regular Celeste which I've nearly 100%d xD