I was suffering a lot of stuttering problems since the v23 update, I ended up factory resetting the quest after trying most other things which fixed most of it.
I can run Alyx pretty well now on the following settings
In streaming tab:
refresh rate 90hz
quality - high
bandwidth - 80mbps
sliced encoding - on
extra latency - on
after a lot of messing about in the steamVR settings menus, i have accepted it is best to leave all render resolution settings to auto and let virtualdesktop dictate that with its low/med/high option
The other issue i was having was alyx was that at 90hz the game would seem to be locked at 85fps max and dipping below a lot.
I have not looked into which fixed it but it was one of 2 things:
-setting the desktop refresh rate to 72hz so it is different to the in game refresh rate
- turning off vsync in the nvidia control panel and turning on low latency (its more likely this as when in game, my monitor resolution was switching to 1980x1080 85hz )