I was pleasantly surprised with the files of my 5DS R. The noise control, sharpening latitude, shadow latitude, and over all color and contrast of the images where better than I expected. I thought there would be an improvement, but not as much as I saw (especially coming from a 1DX). And I was also a little surprised you did not have one.Although, I can see were all AF points being good to f/8 on the 5D IV would be very helpful for you, and the slight PP focus shifting ability in your type of shooting may come in handy.
I think the 5DS R is a really good camera that is down played by many. It is an over achiever that is pegged as only good for landscape, large print, and higher end studio work. I think there is more to this camera. The ability to crop heavily is a plus, but the ability to crop moderately to achieve a good composition is a big plus when coming from a 1DX perspective. Cropping an 18MP image even moderately would significantly reduce the file size to limit print sizes too much... I think your 5D IV will also address this concern.
Enjoy your new cameras, and I hope the 5D IV turns out to be an excellent camera as well.
Pat