You could add a power head for more circulation if you want I don't think it would hurt anything. I am just unsure if you need one since I don't know exactly where/how your plants will be placed in the tank to obstruct water flow. Just use your discretion.
As for the light, you could put it on the legs but adding more distance from your light to the tank will lower the effectiveness of the light and amount of light that gets into the tank. Fortunately the plants you listed should be fine with low light so you should be able to do whatever you want.
Personally I have glass tops with the the lights sitting on them. Some of my fish tend to jump or splash and this helps keeps the lights from getting any water on them and also keeps the fish in if they get spooked for some reason.