I've updated my B450 Gaming Pro Carbon AC. Updated BIOS first, still with my 3600 in it to try it out. Only issue was that Windows forgot my Bluetooth keyboard so I had to re-add it. Strangely I got 21% higher multi and 24% higher single scores in Cinebench with the 7B85v1F1 BIOS with my old 3600 fitted. Maybe there was a setting that I had before in the BIOS that was hamstringing the set up and after the BIOS install and reset it got wiped.
Then fitted my 5600X and all looks good. In a Cinebench run it's boosting to 4,649 single and swapping between 4,574 & 4,599 during multi core across all cores. I did notice that the Powers -> Package number in HWINFO was very high - about 116.75 W whereas my old 3600 only went to around 70 W. The 5600X gets a lot hotter too during a Cinebench run - up to 75 compared with about 53 for the 3600.
Now getting 40+ FPS over New York at 4K in FS 2020 with an RTX 3090. With the 3600 it was about 19 FPS - not sure if this is solely the new CPU or this strange boost in performance even with the 3600 still fitted after the BIOS update.