Green Terrors have as much personality as a red devil, and will hit the glass just as hard. I have both and they go nuts when your near their tanks and both will bite hands if you don't watch out. GT can go in a smaller tank. If you've got a 75 you could get either. If you don't have a 75, get the GT. In all honesty the only difference between the two is size and color.
What size tank? If it’s big enough the cichlids may work. The danios may start to disappear , or be left alone.
A school of 12+ is more impressive than merely 6.