The spot AF seems like it will be a negative for me. It sounds like you are doing the same thing I am doing, trying to find the balance in the camera for the right settings. Last weekend was the first real outing with the RF 600MM F/4 and the R5 and I came away with a list of things I need to sort out for the AF.

One other thing that is puzzling is that the settings in the body seem to randomly change. For instance I was in AV mode I have it set in Auto ISO and suddenly it switches to a set IS0. Another time I am shooting and the picture seems washed out and I find that the camera is set to Kelvin. I still believe it is an ergonomic issue and I just haven't gotten used to the body.