GrapheneOS and CalyxOS are very different. GrapheneOS is a hardened OS with substantial privacy/security improvements:
grapheneos.org/features
CalyxOS is not a hardened OS. It greatly reduces security vs. AOSP via added attack surface, rolled back security and slow patches.
Compatibility with Android apps is also much different. GrapheneOS provides our sandboxed Google Play compatibility layer:
grapheneos.org/usage#sandboxe…
Can run vast majority of Play Store apps on GrapheneOS, but not CalyxOS with the far more limited and less secure microG approach.
https://eylenburg.github.io/android_comparison.htm is a third party comparison between different alternate mobile operating systems. It could include many more privacy/security features but it's a good starting point.
https://privsec.dev/posts/android/choosing-your-android-based-operating-system/ is an article with more long form comparisons between OSes.
Thanks so much for your insight... I all look into it.... After all I am open to switch.....