Thanks a lot for the input, it seems like it helped a lot to turn on rebar in BIOS, and turn off overlay in GeForce Experience.
Also, I had DCS run by an administrator, and I reverted that back to standard.
And now I am stutter-free completely.
But I must say I am still testing, so I will be back to confirm that stutter with F16 is indeed gone fully. I only did a couple of isolated missions for now, and it all went good.
I will be back with more info, and hopefully, this is a user error, as I suspect it to be. I and Iceman06 have a very similar PC configuration, GPUs are the same, similar 240hz 27-inch gsync monitors with 64 GB ra,m etc... CPUs are different, only