I now have another Pixel 2 (camera app crash issue). I have installed Android 9 (PQ3A.190801.002) on it and it is a clean install, nothing added.
I have charged both pixel 2's (the other running UT OTA-21 Stable) to 100% and put them on the side running on standby.
Both devices are well used so I assume battery life won't be great.
So far the UT Pixel 2 has dropped from 100% to 37% in 4 hours,
The Android 9 pixel 2 is on 84% after 4 hours.
I will continue testing.........