If I have multiple deformation materials on an object, each using the mix option in the materials tag so they lay over the one below in the texture stack, (so that's multiple materials each with a deformation for each object), does the SubD that happens to make the deformation, subdivide the previous deformation's subD? Is Cinema smart enough to only divide the geometry thats needed for the deformation or does it divide the entire object and therefore I don't need to have the deformation tab of the second (and third and fourth...) stacked material re-divide to get a clean deformation?
The material with the highest subs level wins but it will not subdivide any higher than that.
If you want to look at the render-time subdivisions you can add a Cel Renderer effect to the standard C4D renderer and turn on edges.
Then you can toggle the displacement channel of one of your materials on and off to see the difference.