My 4K HDR Sony Bravia (and the very cheap HDMI cables from Amazon!) supports all possible output formats for SDR and HDR10 (no Dolby Vision on my TV, though). So I played a bit with the settings. I have tvOS 11.2.5 beta. These are the main scenarios:
ATV4K on HDR 50/60Hz 4:2:2 - Match Content...