In case anyone is interested, this is what I've been wrestling with.
The i1 does appear to be able to correct for this, if you let it make it's own measurements. I decided to use DisplayCal. It's free, and appears to be pretty good, though I don't have much to compare it to. After delving into the advanced settings, I did eventually produce a decent ICC profile, and I am now using it with mpv. The results are pretty good, but I think it's mostly due to the calibration and not the ICC (which is built on said calibration). Color accuracy is good, but I could have used much larger color patches to gain greater accuracy. I just didn't have the patience to wait more than an hour. Considering the i1 is apparently the fastest colorimeter, I imaging that other meters must take many more hours to complete the same task.
I made several profiles, and tested each one. I finally figured out how to make a wide gamut profile, and made two profiles with that. One with a 3dLUT and one without, keeping all the other settings the same. There was a notable difference in color accuracy between them. The one with a 3dLUT being the better of the two. This is what I am using with mpv. It also appears as those with 3dLUT, Windows 10 won't accept them for its display, Not that it matters, mpv is quite happy with them.
Through my adventures, it is clear that HDR being handled by your display as opposed to tone mapping to the desktop, is an entirely different animal. Even though Windows is in HDR10, that peak luminance isn't fully accessible when tone mapping to the desktop. Windows just isn't allowing it. It's got a tight grip on it's desktop. Maybe in the future an update might loosen it's grip. That said, mpv is providing a very good picture, while not being as sparkly as HDR passthrough. Which is achievable when using jeeb's test build. Once the HDR only option for external players is implemented, I will test the bashiznits out of it
I hope this is informative