LostinROM each profile counts as a separate device, there is no such thing as one global VPN across all profiles. That's why I have two Mullvad subscriptions now. :D
If you use many profiles, I'd recommend to use the owner profile exclusively to install and update apps. You can then push these apps to other user profiles in the respective settings and don't have to install them many times over.
This way you also don't have to worry about error messages when trying to install a different version of an app in another profile (which wouldn't work).