I'm not sure how well the waterfall outlet will work if it's connected to the same piping as the lower outlets.
You might need either a dedicated pump/powerhead for the waterfall, or some sort of restrictive valves on the lower outlets.
Otherwise, I think you would either get too much flow out of the lower outlets, or none at all through the waterfall.
Why not have the waterfall be the only outlet?
I think the rocks and wood look nice, and having plants will fill in quite a bit.