If you find that your turbosmooth modifier isn’t being taken into Unity.
You have to uncheck the Turbosmooth checkbox in the fbx settings, so that it converts the mesh to the high resolution mesh, rather than just the low res mesh.
To my logic, it seems like the inverse to what it should do, but it works!
Yes, Unity doesn’t support modifiers, so effectively the FBX exporter is converting the mesh to polygons for you at export time when you uncheck. For best results you can convert to poylgons first and preview in 3DS max to see exactly what your converted mesh will look like in Unity.