Dynamic occlusion/motion vector disable?

When am I supposed to disable dynamic occlusion/ motion vectors on a mesh renderer?

If a mesh is marked static and has baked occlusion does the dynamic occlusion setting do anything?

How do I know which post processing effects use the motion vectors?

Should I disable it or is the performance impact negligible?

bump…

If a mesh is marked static and has baked occlusion does the dynamic occlusion setting do anything?

bump! would like to know the answer to this as well

?