This whole thread is striking a nerve with me since these seem to be all of the issues i had been dealing with since getting a new 16 inch a few weeks back. Specifically "windowserver" and also these bluetooth issues.
See my other comment in this thread about how i solved "windowserver".
Bluetooth issue was a hw proximity issue for me. My CalDigit hub was mounted right below my Macbook. I noticed when I moved my MacBook's location (still connected to hub), the bluetooth issue when away.
It's worth a try if you have a powered accessory near your macbook and haven't tried this already, but...
I do still get the issue once in a while, but I can now at least just turn the keyboard/touchpad off/on and it goes back to normal whereas before, it happened all the time.
Once in a while I still have to Shift+Option+"bluetooth menu icon" and reset bluetooth module.
I know these are just work arounds, but at least it allows me to get back to work and only have to deal with it weekly instead of not being able to use bluetooth at all.
Edit: just upgraded to 12.0.1 and noticed Shift+Option+"bluetooth menu icon" to reset bluetooth module is gone!?