Owners and billers
Each team has an owner and a biller (in case the team subscribes to a paid plan). You can transfer team ownership to any team admin in team settings. Any admin can subscribe to a plan to become biller. If there is a biller already, and another team member subscribes to a plan, previous biller's subscription plan is cancelled and new plan becomes active immediately.
Projects belong to teams. If you would like to transfer project to a different team, make sure you are added as admin to the project and both teams, then navigate to project settings and change "Belongs to team" setting.