What can each member of my team do?

What someone can do follows from the role they hold, not from who invited them. An owner can do everything, including managing members; a manager can work on the company record and invite people; a member can use the account.

The role is set in the invitation, and it can be changed afterwards by an owner.

The last owner cannot be removed. Otherwise a company would be left with nobody able to act for it, so make someone else an owner first, then step back.

If this did not answer it: support inside your account is under development, and until it opens, this says what does reach a person.