Hi Larry,
The 3d textured mesh is a representation of the surface of the model used for visualisation and presentations. To create the 3D textured mesh one use geometry and texture that; moreover, a slpk format contains more level of details hence more information added to the size. Therefore it is safe to say that the size of the inputs it is not directly correlated with the size of the mesh.
As per the second question please see my answer in the other post you have created 
Cheers,
Ina