I played tournaments and the league in the Middestates section this year.
You can't self-rate until you have a team.
You don't need a rating to play in tournments. If you do have a rating(self or otherwise), you are not allowed to register for tournments below that level.
The standard of play is higher in leagues than in tournaments. In the league, only top few guys in the team play singles usually. In 4.0 tournaments, you see a lot of 3.5s and even 3.0s playing.
Someone with a .500 record in the 3.5 league could win a 3.5 tournament.