For me the EOS R is not the right compromise. When photography is incidental to the occasion I like the M5 with the 22mm pancake (or 50mm 1.8 with adapter). The rest of the time I prefer the 5D IV.

A point of ergonomics not too often mentioned is that the mass of the camera plus lens is helpful for eliminating effects fine tremor of the hands and fingers, at least until they fatigue.