Here are the different ways to allow team collaboration and editing of trips within the team: 

To enable any team member to be able to join and edit any itinerary within the team (even if they are not the Owner of an itinerary), the Admin will want to select "Any Team Member" from the drop-down menu under "These roles can edit any trip".

Note: An "Organizer" can change the Owner of any itinerary. Even if "Any Team Member" is selected for who can edit, there are a few restrictions on what "Team Members" can edit such as changing the owner of an itinerary, changing the presenter if multiple profiles is turned on, etc. 

If you don't want everyone on the team to have the ability to join and edit access to any itinerary, you can assign the role of "Organizer" to the Team Members you want to have editing access and then update the team function to "Team Admin and Organizer" under "These roles can edit any trip".

If you only want the Admin to have access to join and edit any itinerary, you will want to choose "Team Admin" under "These roles can edit any trip". It is important to note that even if "Team Admin" is selected any Team Member that is labeled an "Organizer" will still have the ability to change owners of an itinerary and other normal role permissions associated with being an "Organizer".