Just as a follow up - you can use houdini apprentice to make VDBs and export them for free - follow the tutorial on Entagma if you haven't already. Varying the internal density with noise it quite important to the look - don't make your volume step length too small or density too high for clouds - you'll see the voxels more. Start with density of 5 and a volume step length of 1.
Win `10/ Cinema 4D R17 / 2 x 780 GTX 6GB + 2 x 980ti