The PPD file located at "C:\Windows\System32\spool\drivers" ("x2UNIV.ppd") on the Windows workstation is the always same no matter what option I set (Finisher installed, punch hole, etc.). And it is very different from the "Generic PPD" I downloaded for the 7845.
I tried to give the "x2UNIV.ppd" to the CUPS server, it accepted it and I could specify the installed options via the web GUI.
Linux clients can still print correctly (without the need of a driver nor PPD).
But Windows clients (with the "7845" profile) still have issues: a simple two-line .txt file prints 16 pages of "@PJL XCPT" code.