I’m not sure how/what you are doing because the way I’d approach it none of the verticis would matter. Mesh swaps are instant. Niagara can make the transitions from one mesh to another without any consideration for original/final vertex positions…
Regardless. Are you triangulating your meshes Before importing to ue4?
If not, do that. You should get the exact same mesh you see in the DCC in unreal if you do so.