[knubbze]

https://kodi.wiki/view/Log_file Literally the second google hit on my search for Kodi Log.
nVidia Shield hot fixes are, AIUI, released by the Shield TV developer team to fix bugs or add functionality in between major public releases, or to test bug fixes with the wider community. Not sure what you mean by 'unofficial'?

AIUI there are issues with the refresh rate app in Amazon Prime Video (for at least some users) as the app refresh rate checking as an attempt to circumvent DRM and gives an HDCP 2.2 error.

Yes - the lack of app support for the Android TV refresh rate API is annoying (just as it is on Amazon Fire TV - where Netflix also doesn't support application refresh rate switching. (The Netflix app on Apple TV does) 

If you use Netflix and Amazon Video within Kodi {using the respective addons), automatic refresh rate switching works. 

Ah - does this work with the UHD Dolby Vision streams?

Not sure, I don't have a 4K/HDR TV yet.