What method did you use to customize the torbrowser in 14-DVM?
I think the cleanest way is to just create a new DVM template whose name does not end in *-dvm, let’s call it whonix-ws-dvm2. Then it behaves like a traditional qubes DVM template (i.e. all of home persists, torbrowser isn’t recreated on startup every time). Then for updates and customization, you do them from within torbrowser in whonix-ws-dvm2 (and torbrowser’s internal updater preserves customizations!).
The result is 2 DVM templates:
a) the original whonix-ws-dvm. dispvms based on it have the default experience, good for troubleshooting, minimal fingerprintability
b) whonix-ws-dvm2. dispvms based on it have a more comfortable, customized experience.