As far as I know the app (APK) is present on the phone only once regardless. You could probably see this by installing an app in one profile and trying to install a lower version of the same app in another profile. This should fail due to downgrade protection.
App data on the other hand is per profile.
juri can someone shed me some light how safe it is to share apps from root user to 2nd user?
With root user you mean owner profile or not? … since GrapheneOS is not rooted normally. Pushing apps from owner to secondary users is fine.