Hi, B6 here
Using the new LG UHD UP970 i've finally been able to use the Masciola's test patterns on HDR GAME MODE, this is what i've found:
On Low Black level Clip test : from 0 to 2,5% remains invisible, so they're clipped, but at the same time it allows the highlights to be less clipped than with HDR STANDARD mode, so the thing is, if you use HDR GAME MODE, you'll have to raise the brightness of the game a bit more to do not crush blacks, but also remember that the TV will be about a 20% dimmer anyways, also NOTE THAT DYNAMIC CONTRAST WILL NOT GIVE YOU BACK THE CRUSHED BLACKS!
For UHD playback i've found that since the HDR Standard calibration is just pure sh*t (Since there's no 2 point calibration), the best way to get a bright image is to use HDR VIVID, but you have to make a few changes to it, to delete all that saturation and broken image quality
Since on HDR VIVID the gamut is locked to wide, which is incorrect, you have to low the color to 45 to match the Normal (Automatic) color setting from HDR standard, plus you have to low the Contrast to 90, dont worry, since this mode is about a 20% brighter than HDR standard anyway, taking away those 10 points will do nothing and still will look brighter than HDR Standard, put colour temperature to W50, that will give you the closest white to D65, also low the sharpness to 20
The result is almost the same, colours clips at the same point (Without those tweaks, it clips really soon), color looks the same, but with the difference that you will have a brighter HDR image