Looking into that as an alternative for my dying pixel 3a but CalyxOS is to GrapheneOS what OpenBSD is to fedora when it comes to security. Both are good for updates and common security features but grapheneos has implemented security features that are a decade ahead of other Androids. Hardened Malloc, Playstore Sandbox instead of MicroG, Memory Tagging extensions, Selinux, bootloader Security, etc.