Welcome to Android Central! Does this all happen in Safe Mode as well?
https://support.google.com/pixelphon.../2852139?hl=en
I've seen other threads about battery drain on Pie for the Pixels, without any clear explanation yet. At first, I thought I saw some hit to my battery life, but I think it's settled down. This makes me wonder if it has to do with Pie's more "intelligent" battery optimization (which, over time, is supposed to figure out which apps you don't use often, and essentially put them into a hibernation-like mode). I'd give it maybe another couple of weeks and see if the battery drain persists.