Thanks for the suggestion, Tidy Plates does work for the class purpose, as class colored bars rather than icons. Still acceptable!
Thanks to guidance from BannZay I was also able to get PlatesClasses working, which includes and goes beyond the functionality of PlatesMaster. As a note for future users, I had incorrectly installed it. It has to be downloaded via the "Releases" on the github pages.
To further clarify, PlatesClasses puts a class icon next to nameplates, and also has good totem icon features, among other things. So that solves the class icon part. Left unresolved for me, as yet, is arena unit IDs on nameplates. There is an addonI found on warmane þthat purports to do so (https://forum.warmane.com/showthread.php?t=413940), but it doesn't seem to work for me. Has anyone successfully used it?