I’m not entirely sure how your set team is decided for PVP, but it would be nice to allow you to pick your own characters. This would allow for a strategic team to help defend your PVP score, even though the controls and attacks are decided by AI.
The last team with which you win a match in an event will be the team others see when they come across you in their queue.
Exception: teams you beat will see the team you used to beat them in their retaliation (red) node.