The default teams are built and ready to compete against you!
At release, there will be 15 teams (you make 16) in your single-player league. Of course, you are welcome to make as many teams as you want for a full 32-team league!
The 15 teams will vary in competitiveness to try and help with some balance.
Remember that you can build/create as many teams and playbooks as you wish to have a 32-team league.
Cheers!
The Management Team