I own a basic set wii u
I have an external hard drive which the wii U detects, and save files are saved there automatically.
But I can't buy big games online because the Wii U tells me I don't have enough space, because it uses the System memory as install location instead of the external hard drive.
I can move all the things I have in the system memory to the external hard drive, but that would only free up like 3700 gigs, and I need over 4 for Kart 8. As far as I know it should be downloading them directly into the external hard drive.