MF, I've been playing with Nik for a few years now. What I've learned so far is that I have to be very careful with Dynamic contrast, Detail extractor (or fine structure slider) and Tonal Contrast. It is the use of sliders and control points that are very important and I have to get better at. I'm still missing CNX2 with Nik's U point Tech and Selective tools and still use it for my older cameras .
Re: Chair image, skies are where I find most of my posterization . Of course sharpening artifacts which can be made even worse, more obvious, with some Nik PP.
I will be very interested in your findings

Cheers,
Tom