Couple of days ago I was playing around with graphics settings and running built-in benchmarks. Was using this nice guide of what to adjust first.
And what I learned was kind of counter intuitive (in my case at least, I have very weak CPU paired with mediocre GPU):
The more I lowered graphics settings the worse things became, what I sow was that lowering load on GPU more load was hitting CPU, on lowest settings stuttering and delayed objects load was the worst, while FPS still was around 60. So I increased graphics settings, FPS dropped to around 40, but overall gameplay was smooth and objects was loading much faster, and CPU load dropped from 100% to around 70%.
Not sure what conclusions can one make from all that, is it game using more CPU on lower graphics settings, or something else?
Anyway I suggest you check if your CPU is not to much overloaded and maybe you can pass some of that load on your GPU by increasing some graphics settings.