You definitely want to have the heads firing from the front top. Using a triple head would be nice if placed top center front but you will see it so that is a users choice. Me, I would because you'll get your best coverage from there.

I operate mine 5 times a day for 16 seconds each time. It really keeps the humidity up for the Dart Frogs but would be too much for a tree frog. Duration and number of time a day will be something you'll have to experiment with.