No, in fact the tangent binormal generator will need normals already to generate tangents.
The thing is that it largely depends on what kind of normals you want. There is no one math answer. We’d even have to know more about the mesh you are building to even make suggestions, really.
Edit: and 9 times out of 10, the code generating the mesh has a better idea of what the normals should be than any kind of post processing.