Define "good cloud"...
If you want decent enough clouds to impress onlookers and still have good, dense, hot vapor for you to enjoy, get yourself a low profile RDA with a small chamber that has a slightly restrictive direct lung inhale - or one with an airflow that can be adjusted that way.
If however you want to vape up a room in a hurry and wow a crowd, you'll need more air, therefore more power, and consequently a build that can convert all that power into clean vapor without dry hits: the less restrictive the airflow and the bigger the chamber, the more vapor you'll need to mix more quickly with the extra air that passes through the atty. You'll certainly be disappointed with a very airy, large RDA at lower power.
Me, I only vape at 35W-40W with small "flavor" attys, and while I wouldn't win any cloud competition, my setups spew out more than enough to be taken seriously.