Just the one observation from me that might be more related to my style and skills rather than a technical issues.

At slowish shutter speeds, I find that my keeper rate with the EOS R is noticeably higher compared to that of the EOS 5D Mk IV. This is when shooting at the 400mm end of my 100-400 (IS on) with a SS of less than 1/200 sec.

So, if I were to be shooting a lot of stuff without a tripod, at marginal shutter speeds, at long focal lengths, I would favour the EOS R over the 5D Mk IV.

Cheers

Dennis