I know in GrapheneOS that the Google Play Services are sandboxed and you can install them in a specific user profile, but I’m not sure if doing that still gives you notifications across those profiles

Hopefully someone with a little more knowledge of this can help? lol

It might be a good substitute for some. Some features like contact and storage scopes are missing, and IMO they’re pretty cool Overall just worse privacy and security compared to Graphene

By default, sure. But uBlock is way more powerful when you configure it. Seriously, take a look at their wiki. I doubt that Brave lets you choose exactly which domains to connect to on a per-site basis. And do you really want an advertising company to make your adblocker? They’ve done shadier stuff.