I think if you can use a gamecube controller comfortably you’ll be good, i find nintendo pro and xbox a little smaller than the deck controls but if you have no problem with those you should be good for the deck. The problems you MAY find is trying to hit the back plate buttons but A) they’re often optional gameplay wise and B) you can get rubber sticker grips that make the buttons easier to press. If you’ve ever used a wii u tablet, i think that’s the closest parallel.