The only technical limitation I have encountered using these ROMs is related to GPS: my position is often lost and I need at least multiple minutes to gain it back (or sometimes it never comes back, depending on where I am). This is likely related to not using Google's location services, even though I have turned on all settings like using WiFi / bluetooth to improve the location accuracy. I tried every advice I found online, without luck. Somehow the issue is a bit worse on Graphene, as my position is lost every time I close the Maps app, but it may be related to the phone and not the OS.
Pixel 8 works amazingly with Graphene's new network location feature. Position fixes are SO MUCH FASTER. It is truly a gamechanger. First it was Wi-Fi only, but they just released cellular location as well. They provide a proxy to Apple's location services.