Well, we have a list of compatible drives, so you could pick one from that list. It's hard to say which drive will be durable though. You'll need to look if you can find something about that in reviews or something.
As to your questions of which type of games can be played: I am afraid I don't know. They will probably work using some sort of emulator, but I imagine some games won't work.
It is not possible to use a networked disc on the wii to play games. You can play videos though.
I have never heared of ripping directly to the wii system memory. Perhaps they meant an emulated NAND?