I have 1060, I have smooth fps from act 1 to 3. But once I arrive at Arcx, I notive fps drop. I can still play it ofc but it is nice if I can boost the performance during act IV.

the game sets my graphic setting as ultra high, should I change something in order to gain better fps?

ok, so I'm not alone with this.

I have the same experience. I got massive framedrops starting the first big encounter (voidvoken) in Ark.

Hope this won't stay for the whole act...