AddForce best timing in regard to PhysiX simulation?

Hey guys, I have a straightforward question.
My project requires the most precise PhysX collision available for UE4.
I am using CCD (continuous collision detection), and I use AddImpulse each frame.
The AddImpulse will be called on different objects (UPrimitiveComponents) that will collide with each other.
What Tick group is best for calling AddImpulse on these objects, PrePhysics or PostPhysics, and what is the reason.