Here in the U.S. there are no set rules for tournaments. The targets and distances are up the organizer of the event, but all of them usually use some sort of knock down target system. The targets range in size from approximately 1 3/4" up to 5". Paper targets are also used. There is usually a competition shot at 10 meters but there are other events shot at longer distances (gong shoots,etc.). Sometimes there are woods courses where you shoot at targets in trees. Speed shooting contest also happen.
Here is one link to a discussion on target sizes. There is also a video.