Okay thanks. I feel like it would be difficult to move and dash with the same hand, but I dunno, it depends on what you're used to. I always play these games with controller so I find it hard to use my own judgment here.
I just booted up Celeste to check, and it also uses Z, X, and C as the primary buttons, so I'll probably leave the defaults as-is unless a lot of people request another specific setup.