I never saw any shutter shock from my A7IV, and I use it a lot with full mechanical shutter with my 50 f/1.2 and Sigma 85mm f/1.4 DN. With the 50mm the AF is definitely fast enough, with the 85mm the lens is most likely the bottle neck, not the body.
If the sound of the shutter is annoys you is a personal thing, however, I do know my kids don't care.
It's your money of course, and if it makes you happy >> go for it, but the R9II seams to be a bit overkill to me.
