I have 3 wiis all with 128 Gb sd cards all formatted as fat 32. Also all have 1Tb harddrives plugged in also formatted as fat 32. Google fat formater you'll find the program the raspberry pi people use this program to format large sd cards and drives to fat 32. I have not had any issues running any of my games threw this set up have 500 plus game cube games and 60 wii games on hard drive. on the sd card have every NES, SNES, N64, GameBoy, GameBoy Color, GameBoy Advance, Sega Game Gear, Sega Genesis, Sega Master System, Sega Cd.
My point here is 128 Gb sd card formatted as fat 32 works fine