External authentication and concurrent licensing

We are upgrading from FMS16 to FMS19.  We let our license agreement lapse and now are having to buy new Filemaker 19 client licenses "for Teams" (with the server included).  We previously had perpetual named-user licenses, but are now considering buying perpetual concurrent licenses (at about half the number of the named-user licenses).  We use external authentication (active directory) for our named-user licenses.  Please explain any differences, if any, between active directory authentication for named-user and concurrent licenses?  How does it work for concurrent licenses?  Is the FMS configuration different?  Thanks in advance ...