The 840 uses different firmware to the 520 and you can’t disable the VP at all. You can however access the file system as you described, so my workaround was to edit the XML files for the map themes and make the arrow for the virtual partner 100% transparent. The VP is still running of course, but that does fix most of my gripes with it.

I’ll have to check if I can do something similar for the sounds, but I’m not sure it will be possible since it’s just a beeper and I don’t imagine there are ordinary sound files that can be edited.