It isn't the driver, it is the application making the changes, Application over-rides driver, not the other way around.
You can somewhat disable that by turning off some needed things in the driver so it can't occur, but then you lose more than you gain, for instance any newer version of MS products will have incorrect and not working options, like these in MS Word.
You would need to try disabling SNMP completely
And Advanced Printing Features
Change the Paper to staticly stay as A4 in Print Defaults as well as Printing Preferences
And there still won't be any guarantees, especially since you specify a driver way older than Windows 10 should have, and the fact it really sounds like MS is the problem anyway (It is using Letter, not A4 as the default paper)
If you want to change MS Office, you change MS Office, not anything Xerox
Driverversion: 188.8.131.52N 2011.06.16
Yes, I know it is old, but this is the driver we have found to be working best in general.
One important issue I can't figure out how to fix is that Windows 10 driver overwrites default settings when printing from Microsoft Office, choosing letter instead of A4 among other things.
From Internet Explorer going to print properties gives me a setting identified as "Internet Explorer Settings" (which I haven't configured) with "Letter" as papersize
Printing for Outlook does the same - only "Outlook Settings" instead.
How to make the driver stop thinking and just print A4 regardless of the application?