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) 

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