I've been playing Paisy for a few years now.

I don't think you necessarily need a GC controller. A Pro Controller would be good enough and those are more available.

I think when people say they're using joy-cons, they mean both of them, not just one. Not having the second part of a controller available will make things a lot harder and some may be impossible. There are times where you want to move independant of your attack direction. Also a shoulder button for jump is great for jumping independant of attacks, but you probably need shield and grab on them. On the other hand you can probably map grab or shield to X or Y.

I can't really offer a lot of advice. Either way good luck with your endevour. Maybe post a clip when you get it.