QuickTime Pro will not allow you to play any more types of files than the regular QuickTime Player will play. What the "Pro" option gives you is the editing and exporting features.
You can change your DVD region five times after the original setting. The
VideoLAN Media Player does not rely on Apple's region manager and should play a DVD from any region without asking you to change. It is still beta software and it's being written by a school in France, so it's not like regular commercial software, it does have some rough edges. But, it's always played the Region 2 DVDs I have on my Region 1 PowerBook.
-Doug