Waterfalls recycle in-vivarium water and can be sources of bacterial growth, and aren't used much. With regular cleaning and maintenance, along with changing the water, they can be a great visual accent and do help humidity.

Foggers are used to help with humidity. Dart froggers like 'em.

I personally use a mist king system for various species, but was using a fogger for a while in a single viv for my ornate horned frog. The mist king is still a very fine mist, almost a fog, but I find I get better droplets formed for my cresties to drink with the mist king. Also having a huge water reservoir is easier.