As a general rule, one design team is more than enough. You’re better spending any extra time on other activities, from school work to just having fun.
This is spot on. Work load can vary by project team, and by your role on that team. Time commitment for Freshman tend to be less than for sophomores, juniors and seniors who tend to be system leads. The teams also very in sizes, so that can impact workload. I would recommend you check out a few different design teams, before committing to one. Sometimes it’s the members of the team, that’s more important than the actual team project.
Finally, a year or two on an established design team, will better prepare you for starting a new one.
Good Luck!