Tournaments are supported in TeamSideline.
The playoff module supports single elimination (up to 18 teams) and double elimination tournaments (up to 24 teams). Note: You can create a division without a regular season scheduule.
For pool play you can create the tournament as a league, and add the different pools as divisions, and then have a elimination playoff as another division. You can use manual cross division as your seeding method to pull for the pool play divisions.