Small update: the new AMD 7900X + 1660 super PC keeps giving me problems with my Alienware aw2518hf monitor, so I tried to buy a new 27" 2K 144hz 8 bit VA monitor without FRC but the situation doesn't change, massive dizziness.
Today I tried connecting the PC to my LG B8 OLED TV and with that the situation improved drastically. I need to do more tests because I still have some dizziness/headache from yesterday, but it seems perfect with the OLED TV.
I was already planning to buy LG's new 27" OLED 240HZ (27GR95QE) however it's an 8bit + FRC.. so I'm considering whether it's better to buy the Alienware AW3423DW which is a 10bit?!