is there any problem to use the BVH4 MB object split tree with both static and moving triangles? I assume not, but how optimal is that compared to, let's say, using two trees: one for static only (where we have more config options) and the other for mo-blurred?
Motion blur results in reduced performance as Embree does not support any per triangle precalculations when doing motion blur and has to interpolate bounds inside the BVH, even if you store only or mostly static geometry. If you have much static geometry, building two acceleration structure (one for static and one for moving geometry) makes sense. You could then intersect them one after the other and should get a performance boost of around 30% if you mostly hit static geometry.