After constant fiddling over the last month, I came up with this for color space -- and keep in mind I don't have a PS4:
Auto for HDR
Native for Gaming (1080p, non-4K/HDR*)
Custom for all other content
The Custom settings I took directly from Rtings' calibration settings. It took several minutes but I plugged all of their values in, plus white balance and all of that (I also use their white balance settings for the other modes) -- and IMO the result really gives you the most satisfying color range...at least for, say, Directv/cable viewing. It makes Warm2 (which they recommend) less "yellowish", it's also less saturated/overpowering than "Native" but warmer and better balanced than "Auto". Again, though, I only use this for SDR as Auto & Native work better on those other modes. Still I think it's worth a shot to try because it results in a terrific image when I'm watching broadcast content, Blu-Ray, or Vudu and Netflix 1080p stuff.
Smart LED I have set to Low on pretty much everything. Too much "blooming" from light to dark scenes when playing back a Blu-Ray. The scene in ALIEN when Dallas in the air ducts works when Smart LED is set Low, but High makes it almost unwatchable. In general, IMO Low is a good compromise between having it off and having it set too aggressive on High...but maybe I'd feel differently if I was gaming in 4K.
Dynamic Contrast is off for everything -- except UHD playback. I still find I need it, albeit set to Medium, when playing back 4K UHD discs on my Oppo. Image should pop more than it does and I've read DC behaves differently on HDR/4K than it does SDR, where it clearly does impact the image to a negative degree. I don't go aggressive using it but Medium or Low seems to help a 4k image that seems a little more washed out than it should be otherwise.
*I haven't used 4K, HDR for gaming yet so I know that will be a whole other deal. I'll deal with that when I get to Scorpio or whatever lies ahead