The functionalities in Team Plan and Domain Plan are the same, the difference between the plans is how teams are managed.
In the Team Plan, you are in a team where you can invite coworkers to join and use the subscriptions you have purchased. However, they can access DriveWatcher without invitation and create a different team, with its own billing, number of subscriptions and members (Note: you cannot be in more than 1 team at the same time, although you can receive notifications from other teams).
On the other hand, in the Domain Plan, all the users in your domain who access DriveWatcher will join your team automatically, and they will be able to use the subscriptions you purchased (if there are some available). You would all use the same billing and subscriptions.