Compatibility with Android apps is also much different. GrapheneOS provides our sandboxed Google Play compatibility layer:
https://grapheneos.social/@GrapheneOS/113459782313987260
Can run nearly all Play Store apps on GrapheneOS, but not /e/OS 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.