Guests are able to view and work on Content that's been assigned to them on the calendar but can not Publish content or create Social Campaigns or social messages. Content they create is limited to Draft or Pending Review status.
Team members with the User role can also be granted Admin access. Users without "Admin" access will only be able to access the Social Profiles in the calendar's settings.
Team members with the Admin role are allowed to access your CoSchedule settings.