HDR and Dolby Vision

[Case]

I’ve been reading up on HDR and Dolby Vision, and the various sources are either inconclusive, or contradicting, or making unsourced claims. As Dolby Vision is a kind of HDR, does that mean that any HDR device can read Dolby Vision as HDR, like a layer that can be ignored if not ‘understood’? Or would the Dolby Vision be a separate version?
Does a UHD Blu-ray with Dolby Vision have multiple versions of the content on disc, for the Dolby Vision users vs. HDR10? Does online streaming video with Dolby Vision titles (Netflix, Amazon, iTunes, etc.) stream something different to people without Dolby Vision capable screens, as sort of a handshake negotiation, compared to other UHD users?
Can you help me understand how this works?

[usually_quiet]

I think this video does a fairly good job of explaining static HDR vs dynamic HDR: https://www.youtube.com/watch?v=YBKSCoKLqA0

HDR10 is the static metadata standard which all UHD Blu-ray discs with HDR content currently use. Dolby Vision is the only dynamic metadata standard available for UHD Blu-ray discs at present, but it is never the only option provided for HDR. HDR10 is also provided. I think all current HDR TVs are designed to use HDR10, but only some can also use DolbyVision. HDR10+ and HLG are other dynamic HDR standards in competition with Dolby Vision for streaming. I don't know if it is possible for streaming apps/hardware to automatically determine the best type of HDR that the TV supports or if the user must provide that information during setup.

It's sort of like the old HD DVD vs Blu-ray format war all over again. Nobody knows which dynamic HDR standard will ultimately prevail.

[TheFamilyMan]

My LG OLED will auto-pick what it considers the best HDR format available from the source and use that. I have not seen any user option for this selection, though at this time DV is considered the best. That being said, I really can't tell much, if any, difference between HDR10 and DV when watching such content. It seems to me what matters most is the quality of its application: a well done HDR10 looks better than a mediocre DV and visa versa. But I must say watching a good quality 4k source with well done HDR is mind blowing on that OLED TV, especially when a UHD disc is the source. Currently very few (and costly) UHD disc players support DV though DV UHD disks play fine on all UHD players and provide HD10. Note that UHD discs will not play in standard bluray players. A few streaming service provide DV UHD content, but it's limited to their local productions, e.g. "Stranger Things" on Netflix. If a display device is not HDR capable, it will play content which has HDR, though obviously without the HDR enhancement. I don't know how all this is accomplished, but if you really want a deep dive on this subject, go check out AVSForum.com; they've been bashing this stuff about for a few years now. As mentioned, HDR is a format war that's still unfolding.