I own a 75NANO91 for few weeks now (which unfortunately I can't send back), and I would advise anyone to carefully look at a display unit before deciding, as the color quality is very bad if looked from less than 3m away.
Regarding the local diming, this TV has less than 40 areas handled, it is fine when the picture is full of objects, but quite disturbing when there is only one white object moving in a black background as you could see big chunks of the screen getting brighter and darker. I read somewhere that the highest model has more dimming areas.
Regarding the 4K120 it is nice until you realise that it only works in degraded colors if you don't have a full HDMI 2.1 chain.
The LG NANOCELL are nice on paper or from a distance, but not in practice