Are the Wii Classic Controller Pro gamepads usable in RetroArch ? I m thinking of buying one but dunno if they are well supported in emulators.
Yes, very well supported and autoconfig detects and maps it and works great. It’s a superb controller in it’s own right, and the perfect compliment to Retroarch on Wii. Get an official one and you won’t regret it. Cheap knockoff clones are notoriously problematic. By default it maps as a “retropad” controller type, with just d-pad plus buttons. But you can just go into Settings > Input > Input User 1 Binds and set it to “Retropad w/analog” and change ‘analog to digital type’ to left or right analog stick (you choose) and it will mirror d-pad actions on whichever stick you prefer.
Thank you! Bought one … will have it next week.
Got my controllers (classic + classic pro) today and tested them. They work perfectly!
Great! Spread the word 
Can I Bind 2 classic controllers? It seem to just bind one to player 1