So iPhone 7 and any hardware that is older than 2017 won't do HDR? I understand the new ones will play 4K, but I guess you won't notice a markedly clearer resolution on devices as small as the iPhone and even the iPad...
The 2017 devices will do HDR10 & Dolby Vision, but at 1080p. Only the Apple TV 4K is outputting the 4K resolution.