I have the same problem with the same CPU and a RTX2060. For me the Fix in:
nvidia-xconfig doesnt do what i want it to, nor does nvidia-settings - #7 by generix
worked in Ubuntu 20.04 but not in 18.04 on the same machine. If it is not important for you to use 18.04 you could try Ubuntu 20.04.
I have to use 18.04 so I am still hoping for a solution someday