Only an 18GB download? Nice that was a refreshing change from 100GB+ downloads.
Here are my observations:
Jesus, that narrow FOV is killing me. I could not play this game without a MOD LOL.
Game draws a lot of power. I was hitting my set power limit of 399W constantly. Most games I play usually draw lower wattage.
Loaded it up, used DX12, maximum settings 4K, full screen. Game plays very smoothly, however I do notice a hitch when an action sequence starts. It is picked up every time something happens on my overlay, similar to yours. Yours does look worse. There was no change in this behaviour whether i was in full screen mode or borderless. The funny thing is, the game is perfectly smooth until that hitch. It's very odd.
I did some
research into the game and apparently the DX12 mode has issues. Given the age of the game, it's not going to be updated. I then decided to switch to DX11 mode, and although I have slightly lower FPS, the game is perfectly smooth with no hitching like what I saw in DX12.
I looked at your videos and although you didn't show what settings/API you are using, I will guess that you are using DX12. Maybe try switching it up to DX11 and see if that helps. I tried DX11 full screen and borderless, both were fine. If I was to play this game, I'd be using DX11 since the FPS are high anyway and it runs so much better.
I'd keep HBAO+ off too, that's a Nvidia black box setting and it may not play nice with AMD cards. HDAO looks fine in comparison can't really notice any difference. I see this is a GameWorks title too, must have been one of the last ones made.
I'm uploading some footage to YouTube so you can have a look and let me know what you think. I'll tag you back in when they are ready, should be in a few hours or so.