Framerate drops

I nooticed huge framerate drops while playing 1080@75. It peaks from 30FPS to 75
I have fresh win 10 pro instalation, with newest graphic card and screen driver installed and sometimes FPS drops lower to 20.
screens with ingame options: https://imgur.com/a/vtI58kM
my PC configuration
Ryzen5 3600
graphic NVidia Gforce GTX 1660Ti
16GB RAM
game installed on SSD disc
GK is connected with HDMI cable to screen.

I was forced to change frequency in nvdia to control panel to 60Hz to minimalize framerate drops, but still have them occasionally.
Sorry for my english, is not my native language and I am out of school for decades

This is how VSync works.
If you have VSync enabled you virtually can only run the game on two discrete FPS values: 1) your current display refresh rate and 2) half of your display refresh rate.

Unfortunately the game is badly optimised, the game engine definitely has some issues and despite that all the environment and monster's visual effects are just excessive. Even on a top end PC fps sometimes deeps to sub 40.

Those "fps drops" occur when your PC for some reason can't keep 75 fps up.
You getting 74 fps -> fps drops to 37.

Disable VSync and limit ingame FPS with other tool, like Riva Tuner.
If your monitor is G-Sync compatible - turn g-sync on.

I bought Display port cable to connect monitor and GK--> still same, exile
Then i lowered graphic settings to default and frequency to 75Hz and it loos fine. Looks like shadow (shadows+global ilumination option) in combination with high setting of antialiasing is doing that FPS drops. For example MSAAx4 with default shadows) works fine for now (still testing)

Looks like MSAAx8 with default shadows works good to me too with rare framerate drops (one in few minutes)