I'm not too familiar with indexiine, but I've tried every other method to get signature patches. browser hax is okay with xampp or kws via android, but I don't know how reliable it is above 5.5.1. I'm still on that firmware, and it's close to 100%. it suffers from the same failure sort of thing that the ps4 does except it doesn't kernel panic if it fails.
you do need an sd card if you want to install things using wup, so I'd get a semi-large one. I'm using a 256GB myself. everything works in both wii u and virtual wii. some people have issues with micro sd adapters. I'm using a full size card with the wii u, but I think my wii is using a micro sd adapter. it may depend on the adapter and sd card itself.