I guess the firmware update officially validates the B9/C9/E9 as G-Sync displays, as Nvidia's latest official driver already enables G-Sync on these TV's.
Nvidia's own announcement with some basics set up instructions. Oh yeah this HDMI-VRR only works with GTX16xx and RTX2xxx cards nothing else.
If you want to get the most out of the 40-120hz VRR display with minimal input lag the thing recommended by the pros is to
1. set desktop refresh rate either 2160p/60 or 1440p/120hz With current HDMI 2.0 GPU's.
2. leave vsync enabled in all games.
3. limit the frame rate by 3 below the vsync so at 120Hz you want a frame rate limit of 117fps and at 60Hz you'd have it at 57fps.
4. optimally using a games built in frame rate limiter is best but RTSS is the most convenient option and works with just about everything.
This keeps the display in VRR mode and prevent vsync lag.
Interestingly Nvidia's latest driver has added an ultra low latency mode they call NULL, this does pretty much the above, you set the low latency mode to ultra & force vsync on in GPU driver control panel, then in all games you disable vsync so it defers to the Nvidia vsync. The end results noticed on blurbusters is the same sub 3fps limit however it doesn't work on all games so the RTSS method remains the recommended path.
Some people have even forced custom resolutions above 4K 60hz so 4K 66Hz etc but I will leave that to others/Google. It would be nice if LG added a 4K 66/70Hz mode just for PC usage.
Lastly LG's PC RGB 444 mode in their TV's can have some banding issues, some it bothers others it does not, if you dont care about desktop text at all and it's purely for gaming just use the game mode.
For best use of game mode you want a console like output so in Nvidia control panel under resolution select Nvidia color settings and change it to YCC 444 or RGB Limited, either will do.