Ideas
"Hybrid Scanline SYNC"* in RTSS, or any transversal stutter might scramble frame-pacing with any vsync implementation*... There were still annoying hitches but no 2-3 sec stutters or pacing issues.
There was one place where it would stutter no matter the settings, setting them to mostly high, disabling SSGI and enabling GTAO with fall off end to around a 1000 were the only things that made it less awful.
Incredibly, lowering settings would f' it up again, specially shadows... felt like draw calls stack up on that specific location, and it was about separating each asset group's calls... but I have no idea.
Neither GPU or any CPU core would get even near being overloaded during the stutters.
Really tried to love the game but it wont let me. Eventually got fed up even with just the small hitches, which are often on tricky sections.
But hey, it might help anyone trying to love it too though...