I guess, but I never tried that since my AVR can defeat dialnorm... The problem with that approach is that every movie has a different value. For example, Ballerina has an insane -15db dialnorm, Black phone 2 is at -4db, Smashing Machine is at -2db.
I don't know. I'm not really an expert audio-wise, and never really compared DDP and TrueHD for frequency and dynamic differences. Other people might be able to answer that one.
It depends. If color accuracy is important to you, KS often messes that up. But purely in terms of video compression, KS is better than Apple TV 99.9% of the time. Movies Anywhere, on the other hand, has much better compression with no DNR and can outperform some KS encodes.
HDR alone will be the same everywhere unless someone makes a mistake or deliver a trim pass from the master