There's no limit! You can be a member or admin of unlimited teams. The limit only applies to teams where you are the owner.
Yes! A recurring task (like 'Feed Luna' that repeats multiple times a day) counts as just ONE task template, even if it creates multiple instances. Only unique task templates count toward your limit.
Upgrading to Pro affects teams where you are the owner. It does not affect teams where you are a member or admin.
No, only the team owner needs to upgrade for the team to receive Pro benefits.