We've touched a bit on the topic of portraits earlier in this thread.
I don't photograph people that much, and when I do it is mostly outdoors, in good light. I found that the Natural Light AWB coupled with the Portrait Picture Control take me almost where I want to be in terms of skin tones for the kind of portraits I take. Here is an example with the Z6:
https://www.getdpi.com/forum/nikon/66012-nikkor-z-24-70mm-f-2-8-s-photos-discussions.html#post787248. And here is an example with the D810, for which I had to do a bit more PP, mostly because the D810 lacks the Natural Light AWB:
https://www.getdpi.com/forum/artful-images-to-share-including-nsfw/54630-street-images-any-camera-2.html#post787158. I am not sure how relevant are these examples to the kind of portraits you photograph, though....
I shoot exclusively NEFs, and convert them using Capture NX-D, with finishing touches (if needed) and resizing in Lightroom 6. I use Natural Light AWB outdoors, and Auto WB A0 indoors with artificial light. With artificial light I almost always have to adjust the WB in PP, but not any more than with my other Nikons. Natural Light AWB + Neutral Picture Control give me pretty accurate colors outdoors.
I turn off noise reduction for outdoor shooting and use it minimally indoors. Again, as expected for a 24MP sensor (in between the D810 and the Df). The sharpness seems fine as well - are you experiencing shutter shock perhaps?
Can you post an example that bothers you, together with the camera settings (aperture, shutter speed, ISO, VR on/off, EFCS on/off, etc.)?