As an admin I can create and manage single user accounts. Is it possible to import existing Gmail accounts completely? With Mail, all subfolders, calendars, authorized lists in Drive, etc?
Yes, that is possible. It is also possible to import data from other email services (like with Gmail) into G Suite. The permits for certain folders/files may have to be reviewed and reset. If needed, we can offer you our support.
Please find more about G Suite in general on this page.