Microstuttering + choppy, skipping frametimes

Some more feedback:

I didn't have MSI Afterburner running when I experienced the issues, but just in case, I removed it entirely from my system and restarted the PC. Still the same problems.

I've also tried (according to advice from one player with similar problems) setting both my Nvidia GPU to Max Peformance mode (from the default Max Power) in Nvidia Control Panel, and setting my whole PC's power plan from Balanced to Maximum performance in the Windows 10 settings. Neither helped. The only reason I tried the latter is because I had a sort of similar, Windows 10 related issue a few years ago where the game Bulletstorm; Full Clip Edition would refuse to run at more than 50 fps with Vsync on, but changing the system's power plan to Max performance would fix it and enable the proper locked 60 fps framerate.

I can't try a wired Xbox One controller yet, but I tried playing the game with the keyboard for a bit (controller wasn't even turned on) and experienced the same problems, so it doesn't look like it has anything to do with the controller.

Can't check my PSU's specs right now (I'll open the case and post them later) but it's just over 6 years old at this point, like the CPU and the motherboard. I doubt it's a failing power supply, since I've been running newer and more demanding games (like Doom Eternal) perfectly in recent months.

Also, another important symptom I forgot to mention - the game's menus that feature in-game roads as backgrounds seem to be locked at 50 fps most of the time, and in some cases, even the actual gameplay is stuck at 50 fps (though the frame limit is 60) until I restart the game or change the graphics settings from one preset to another and back. 

The magic CPU affinity trick (disabing the first core of the 4-core CPU) that I mentioned REALLY temporarily fixes all of the above issues - both the stutering/frameskipping and the 50 fps cap in the menus, but unfortunately always causes the game to almost completely lock up after 15-20 minutes. It's the EXACT SAME issue and workaround that was apparently noted by many players in the PC version of the original game, only the solution isn't quite working for me.

Hopefully this is enough information and the development team can get a good patch out to fix it, it's really souring my experience. And it's even more grating that it seems to be an issue carried over from the 2010 PC release.