1TB formatted to NTFS should work, I don't know about hacking every firmware version, but you can definitely hack the latest one (4.3) so if you have a Wii that isn't on 4.3, just update then you can, and yes, you can play GameCube games with the hack, either using the built-in support for it (if your Wii has it in the first place), or if it doesn't have support, or you don't have a GameCube controller or memory card, or would rather have the games on an SD card or that external drive, I'd recommend Nintendont. Just look it up and you'll find it.