I have an 2016 E6, using the 11.2 public beta
i leave it in 4k SDR
the menus look a little too "crisp" for my taste in HDR modes, plus most of my content is SDR
might loose a little in screen saver, but not a huge loss for me.
it switches up to Dobly or HDR10 when needed. (TV doesn't show incoming frame rate, so not sure about that)
if you're in HDR, it will switch to dolby or standard when playing that.
small annoyance in netflix...
Since i'm in SDR mode, in the description it says "4k" but not dolby/HDR, but it does switch to the correct mode when it plays.
so not a problem when actually watching stuff.
also, the "auto switch" only happens if the app uses apple's player, some apps use a custom player (for example, i think VLC does, but not sure) apple has added the frameworks needed to let them switch, but the apps will have to be updated to take advantage.