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?
An option if you need to use non foss apps with some people is to use beeper or even better selfhost matrix with bridges. Sign in on beeper for messenger Whatsapp sms etc and revoke network permissions or uninstall the shitty apps