Yes, you could do that. You can control everything with a controller, but the remote has more things like dedicated subtitle and audio buttons (if that's important to you). With the controller, there are buttons for things like play, skip, etc., but some functions require opening an onscreen menu to select them from.
Yes, of course you can use multiple controllers, and any of them can control the playback stuff. If you're talking about using a PS2 and PS3 controller, that won't be a problem either because the PS2 controller would be RF while the PS3 controller is Bluetooth.