Can I use any normal FDD in a super wildcard?

Yes. If it has a 34 pin connector just plug it in. If it's a 26 pin you'll need to find/wire up a cable to use a 34 pin floppy.

 

You can also use floppy disk drive emulators in them:

https://www.youtube.com/watch?v=62ZlDgp3FyI

 

If you're using it to play, as opposed to display, an emulator is the way to go. I wrote a tool for the GOTEK that takes a folder of ROMs and converts, splits, and injects into an image for your SD/USB device. It also gives you a list of games and the index for what disk number each starts at. Then you use the GOTEK+Copier like an old jukebox or karaoke machine. Pick a game, dial in the number and play. It's silly but works quite well.