Managers have access to all the features as well as they can add/remove people from the S account.
Collaborators have a complete access to your platform. They have access to everything in your S account. They can't invite people or remove people in your team.
Reviewers have a limited access in your S account. This could be your clients, stakeholders or people from the development team. Reviewers can do the followings.
View all the project screens
View and add comments/feedback on screens
Change the screen workflow status (e.g. from in-review to approved)