Well, after the update I played and completed the Open Tour to get the Audi R8. I can't really report any major visual downgrades (or upgrades) but I did see some flickering lights/shadows in some tracks (Kyalami) and cars. Most of the time these flickering went away after restarting the game.
Some tracks do look more detailed than others, but frankly most of the time I'm looking at the road/apex/car in front, so I really don't care much for environmental detail (and Laguna Seca is a boring environment, let's be honest). There is no noticeable texture pop up, and environmental lights and effects are good: Some track/weather/time of day combinations are really impressive, others, so-so. Also, no fps drops or stutters in performance RT mode.
I do play on an OLED screen, and I don't like the HDR settings with Dolby Vision, so I turned that off.