perhaps its something you missed, but you can use a work profile. put all your google apps in there and its a tap of a button (quick setting pull down) to jump into. then another to turn it off. you get the benefits of sandboxing a bunch of apps, while using the same user profile. its very convenient.
I personally don't use the separate user profiles at all. I agree they are clunky, due to how segregated they are. though with a work profile, and if needed (I don't use it atm) the newly added android feature, a private space, I feel there are plenty of compartmentalisation/sandboxing options available within a single user profile.
Private Space is from Android 15 so GrapheneOS has provided support for it since October 2024 when Android 15 was released. Profiles are a standard Android feature, not something added by GrapheneOS, and are not required to benefit from the privacy and security it provides. Sandboxed Google Play does not depend on putting it in a secondary profile.
I personally don't use the separate user profiles at all. I agree they are clunky, due to how segregated they are. though with a work profile, and if needed (I don't use it atm) the newly added android feature, a private space, I feel there are plenty of compartmentalisation/sandboxing options available within a single user profile.