I know that GrapheneOS has a lot of security features that make it basically impossible to compromise your phone. And that it has a lot of control over permissions and has some privacy features. But it also has a Google Services compatibility that would allow you to use Google services, which would allow Google to harvest a lot of data from you; much less data, but still some. Now OSes like CalyxOS or Lineage have microG which in addition to giving you the APIs, it uses less battery and has the ability to use Mozilla network location to stop google from getting that data. CalyxOS and Lineage don’t have the crazy hardening modifications that GrapheneOS has, but Android is already crazy secure compared to something like Windows or Linux without a properly configured SELinux or AppArmor. Why have Graphene over Calyx?
Sandboxed Google Play provides better security, privacy and usability. Why that is, as well as your question about Calyx vs Graphene, is answered in this Privacy Guides Blogpost.
It says that trusting Mozilla for the location backend is the same as trusting Google. I may be biased or something because I use Mozilla services but that’s just insane to me. Mozilla’s business model is not the same as Google’s. Are there no network based location services for Graphene other tjan Google? GPS location sucks sometimes and I’d like to have a proper alternative if possible.