elchona I feel like it leaks my real IP address.
GrapheneOS fully fixes the leaky VPN issue with all 4 other known Android outbound VPN leaks. Many things aren't covered in our features page, especially specific privacy/security weaknesses we've fixed downstream, but in this case it's covered there: https://grapheneos.org/features#improved-vpn-leak-blocking
Beyond that the only impact that could adversely effect this is your personal configuration and choice of VPN.
elchona can I create multiple separate profiles? (one for each client)
Yes you can, you can also have each user send a notification the current user you maybe using at the time.
There is also an app in Accrescent to help facilitate moving data between users without use of a USB stick for example unless the latter choice works better for you.
Each user does however need it's own independent VPN connection, they do NOT get funnelled through the owner profile, it would adversely affect your privacy doing so as would using one built into router. Each user having it's own VPN install allows exiting from different US exit points too. If you can push to using different VPN providers/mixing and matching say between Mullvad, IVPN, Proton can only help further.
You can install apps from multiple sources, Accrescent where apps are there (IVPN for instance), Play, Aurora Store (this works best for apps with Play Integrity flagging in the store listing but not enforced in the app while having the downside of apps checking for Play as the install source not working properly in some cases, and then something like Obtainium, where you can add multiple sources outlined in their documentaiton, but is especially useful for adding Github app release pages.
Let us know if you need anything else.