Maschell, I've done quite a lot of testing tonight, here is my experience mainly with Smash.
Using one joystick, whether over network or USB, works flawlessly.
Using one joystick on USB and one on Network mostly crashes upon boot of SSMB, however it succesfully launched once for me and despite the gamepads being detected in the wii u menu, i couldnt move inside the game. Sometimes selecting 2 gamepads and applying patch crashes at that exact point (hasn't occured while only using 1 gamepad).
I tried booting 2 gamepads over network - it only detects one gamepad. This is while trying 2 DS4 or 1 Ds4 and one Xbone controller. This is despite the PC client accurately showing and activating the right number of devices.
But honestly, I'm glad the beta is finally out!
EDIT: it appears with SSMB, that even with 1 DS4 there are frequent random crashes. Tested it without HID To Vpad and the game runs fine. Zelda can however run fine with 1 gamepad, no problem.
Also I'm using Mocha --> HID to VPAD ---> game