Same applies for my Series 8 45mm watch. Briefly warm and took a few days to index whatever needed indexing. During this time the battery depleted at a much faster rate. Typically by 4pm it has about 69%. During the two “indexing” days I saw 10% and 13%. It now has what I consider normal battery usage with no changes in behavior by me.
Currently on DB2 and no issues to report. iMessage seems snappier and less jittery.
Can report that RCS is working on AT&T. That being said, I received my first RCS message while not being connected to the AT&T network and without WiFi calling being enabled on my phone. Was at home with my phone on WiFi only and received a message from a friend who has an Android phone. I replied with a heart, text and some pictures. The second message failed (its beta) so I turned on the cellular service to complete the conversation.
Just sharing my experience.