Of course HDR10+ is available, my OP stated it plays in HDR10+ when starting movie from continue watching, tags only HDR10 though when playing from my library.

4K SDR resolution and set match content and frame rate to ON, 4:4:4 if available and make sure you have a quality certified HDMI cable, ATV 4K boxes can be finicky with cables.

First off, apps open faster and are much smoother running, super fast navigation, picture quality is great, good UI and if in the Apple ecosystem the experience can’t be beat.