@L0LIpOp
Because it is like a PC, you can have a video recorded on a dvd, a pendrive or a SSD and you will be able to play it without problems.
With the Wii it's the same, only when the scene started it was limited to have the apps on a SD and...
@L0LIpOp
It is not complicated at all, except for very few apps, most of them work on pendrive or HDD.
The only thing you would have to configure in each emulator is to change the paths that are probably addressed to the SD (games, screenshots...