I've been wondering a similar thing as the OP. I have read a good bit on user profiles but am not quite sure they work how I would like them to. Let me describe my use case.
I'm very interested in privacy as a way of life in addition to security. I have de-googled as much as possible in my life. I have used Protonmail for years, Startpage for searching, Brave for browsing, Signal for messaging, as much as I can.
Apple's privacy policies are (historically) surprisingly good. iMessage, Maps, etc. I lost that when I moved to GrapheneOS so I'm trying to replace that.
I ran into issues where people messaged me using RCS and I never received their messages, so I had to install Google Messages, which I absolutely hated to do, but not corresponding with these people isn't an option. I have tried Magic Earth, Osmand~, and Organic Maps (and have contributed quite a bit to OpenStreetMaps myself) but it just isn't on par with Google Maps or Apple's Maps. So I installed Google Maps as well.
Now I'm concerned that Google has access to my contacts (through Messages) and my location (through Maps, even though I set my App battery usage to Restricted).
If this is a valid concern, how do I get around that? I have not experimented with Users but if I put Messages and Maps in a separate profile, presumably my Messages would just come in as phone numbers and no names associated with them? That's okay but not ideal. Would I get cross-profile notifications for time-sensitive texts from that profile if I'm almost always in my "main" profile? Should I set up just my App stores in the Owner profile and create a "daily" user profile for my regular apps (Signal, browser, utilities) and a "Google" profile for Messages and Maps?
Any advice or thoughts on any of this would be appreciated.