Thanks all for you contributions and suggestions.
I’ve got my 7900 XTX up and running with no dramas. Followed the process I outlined in the OP. I also completed a registry clean to remove any additional entries not removed by DDU:.
Flight Simulator started and worked first pop. At 4k I am getting 60-90 fps. Average would be around 72-5 fps.
Still got some tweaking to complete in MSFS graphics cards settings.