Just finished the main scenario, haven't entered the secret area yet. Have Cygnus Noise.Skimmed through the game, so I didn't get any HP upgrades or anything like that.Cheated only to pass the game sooner.
I don't have a wii u anymore to test it myself, but if homebrews are not visible on the wii u menu I think you can press L + R + minus to open the plugin menu, there should be an option called "homebrews on wii u menu" or something similar