Newcomer here, wish I'd known about GrapheneOS sooner. This is waaay easier than rooting a stock ROM and debloating it. And the added hardening on top of eliminating root access is welcome.
I'm running a Pixel 8 and a fresh install of GrapheneOS presented with minor display stutter/jitter, i.e. frames would appear to drop for a split second when doing something mundane like quickly scrolling a tall menu or even bringing up the lock screen. In the past I would get rid of this by toying with the CPU/GPU governors but this is not an option on a non-rooted device.
I eventually overcame all this with exactly the following settings. Emphasis on exactly. Unfortunately you must enable "Developer options".
Settings
Display
Smooth Display - OFF
Settings
System
Developer options
Force peak refresh rate - ON
Allow window-level blurs - OFF
Hope this helps others.