4:4:4 8 bit is the best option for resolution and minimal banding. 8 bit RGB full is the native format of Windows but it will have more banding with the TV in PC mode. There is no point to being in PC mode if you use a 4:2:2 mode.
4:2:2 is a big quality drop, much higher than 8 bit v.s. 10 bit. 4:4:4 video data consists of three planes each at 2560x1440 and is converted to 4:2:2 by simply resizing two of the planes to 1280x720. Also, these LG's do not handle 10 bit well in PC mode. I see more banding with 10 bit input than I do with 8 bit input so 10 bit is worse than 8 bit even if you can do 10 bit 4:4:4. I use 8 bit for everything on these LG OLEDs when in PC mode, the only point of 10 bit is less banding (or lower dithering noise if there is no visible banding with 8 or 10 bit) so if the banding is worse with 10 bit you should definitely not use it.