Just to chime in here, your recommended settings are not actually ideal, specifically these lines:
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- For LG CX OLEDs (I have 48") you MUST go into WIN 10 advanced display settings and set resolution to 3840 x 2160, you also have to set the monitor Refresh to 120hz (defaults to 30), and enable HDR, Enable Variable refresh rate, enable hardware-accelerated GPU scheduling... It's amazing none of this is on by default or auto-detected. would be nice if LG offered a driver!
- For LG CX OLEDs, in Nvidia control panel, choose Change resolution, in section 2 - choose a resolution of "PC" 3840 x 2160, 120hz refresh. Section 3, override to NVIDIA color settings and choose 32-bit, 10 bpc, yCbCr444, Limited. and apply"
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You don't have to do anything in line 1 except enable HDR, the rest will be overridden or changed by the NVidia driver once you start setting the options in line 2.
Also, don't use yCbCr444, the native color pattern for LCD/OLED is RGB for PC use, you're essentially putting more work on the card / system by forcing it to send a yCbCr444 signal only to be converted back to RGB by the display. You should set it to: 32bit, 10bpc, RGB, Full.
It's also a good idea to set your input to PC mode, this can be done by going into the Home Dashboard, highlight the HDMI input, then selecting the settings in the top right (Press the green button), scroll down to the icon next to the label for the input, select the icon and change it to the PC icon, this will change that input to PC mode which will automatically adjust many of the picture settings for PC use.
Lastly and most importantly you MUST be on LG Firmware version 3.11.25 or higher for any of this to work as G-Sync and Subchroma don't work properly on prior versions with the 3x series cards. 3.11.25 isn't rolled out broadly yet so if you want it you have to install it manually (currently). The Korean and US firmwares are the same, the Korean LG site has the firmware available for download, if you google the 3.11.25 LG CX firmware download you'll find a few places with direct links to it. Once this is setup the LG and 3x series really shines... the display quality and output is truly fantastic. Don't spend ridiculous amounts of money on HDMI cables, it's a digital signal as long as it's rated for the proper bandwidth with the right pins and gauge of wire it'll likely be just fine. I personally use the Monoprice DynamicView Ultra 8K Premium High Speed HDMI Cable, 48Gbps, 8K, Dynamic HDR, eARC cable, the 6ft version costs a whopping $14 and it's perfect. I use these on all 9 of the OLEDS in my house and they test solid for every video, bandwidth, and chroma test I've done so far.
If you want to check your signal from the card (quick and dirty), just press the green button on your magic remote a bunch of times and you'll get a Freesync overlay window that tells you your current signal. (You want to see VRR, 3840x2160P at 120, RGB 10b 4L10) The Hz will change depending on your content. The key here is you want to see 3840x2160P NOT 3840x2160I or 4096x2160I. You want progressive mode not interlaced mode.
There are cases where doing a Nvidia driver upgrade from an earlier version is causing issues here, (it happened to me too), the only way I could fix it was to do a full driver uninstall, reboot into safe mode and do a driver clean (while disconnected from the internet so Microsoft doesn't auto install the driver on reboot), then once back up I installed the latest driver and all of the options worked correctly, then I reconnected back to the internet and everything is happy. (This is a last resort if you can't get your resolution to set properly with all of the noted things above).
If you want the more advanced version with full diagnostics, go into the TV settings menu, scroll down to the Channels tab, highlight the first option (Channel Tuning for US versions of the TV), then press 1 5 times (ie: 11111) that will bring up the host diagnostics screen. From there scroll over to the HDMI mode, and hit Ok, this will bring up the full HDMI signal information screen.
Enjoy!