As a morph you unfortunately can't. A morph is just information of where each vertex should move. The extra vertices a genesis with high resolution has in DAZ are just "virtual" vertices and do not actually exist. You can notice that when you go into tools > geometry editor and see that you can't select any vertex that is not a base vertex. So, if they are not really there, they can't receive morph information.
When you export the mesh to blender with a higher resolution, the vertices are generated for real but then you can't put the information of those vertices on the genesis model inside DAZ, since those vertices don't actually exist there (and thus, if you try, you get the geometry mismatch error).
Edit: Now I remembered a model/prop that had like 1M+ verts when I put it in high resolution and had WAY less than I would expect when I put it in base res, so I may actually be wrong and there might be a way I'm unaware of.