Can anybody keep track of the “Tier 2” UU Wizards?

I’ve read all the books at least twice (except Science of Discworld, but I have read the first two).

Obviously its easy enough to form a mental picture of Ridcully, the librarian, the Bursar, Ponder Stibbons, and even the Dean.

But when it comes to the Senior Wrangler, the Lecturer in Recent Runes, and the Chair of Indefinite Studies they are all sort of just interchangeable labels? Am I not paying enough attention or do they not really have unique characterizations?