Sorry to interject here, but since this seems to be about whether or not TG is good for clouds:
Would it be safe to say Terragen is a good source for "Clouds from Scratch; and one of the most powerful". I noticed a lot of software, including what my friend is using, is sorta based on preset models, somewhat like Easy Clouds. Asking for a friend.
What I gather, and from experimentation, you can achieve pretty much anything you can think of as far as clouds/gaseous stuff, and even noisy water (waterfalls)