Isn't that dunia engine 4 core optimized?
I noticed the same behavior, nice job figuring out how to make it work better.If Crysis 3 is any indication, I think this line of engines suffer from a frame buffering defect. While revisiting it to test my 3080 overclocks, I noticed wildly fluctuating GPU usage and fps, especially in the early shipyard levels. Toggling PhysX between GPU and CPU had not effect. This was with in-game VSYNC on and G-Sync compatible running at 144Hz mode. I had used it to test overclocks on my 1080TI in past and likely forgotten how I got around it. After googling again, I enabled Fast sync in NVidia control panel, capped max fps to 138.
Et voila! Constant 99% GPU usage, completely smooth fps around 120. All of the stutter instantly vanished -- I cried in happiness for the buttery smoothness.
Crysis 3 stuttering | Overclock.net