I'm a little confused the best saturn emulator would be giri giri or cassini.Will either of those play back up copies or only the original cd's

You can use either one. It would be pretty stupid if an emulator only ran original CDs and not backups, don't you think?

Also, Cassini is a hack of an already hacked Giri Giri. So I'd go with Cassini just because it's the most recent.