Gotta say I'm really glad I can outright select Wii U Pro as my controller in various games while using a Wii U Pro controller on to play anyway. xD
Also I made a video of 2 players in SM3DW using both a Wii U Pro controller and DS3 for those interested-
Somewhat surprised the performance hit wasn't as big as I was expecting with more than player tbh, outside of that single player performance seems more or less the same and for the most part cloud shadows seem to be fixed.
How are you getting sound past the title screen?
Maybe it is nvidia only? No idea.