You can get a small pump that will do a much better job than a powerhead. Pumps are designed to lift. Powerheads are designed to push without lifting. Yes, you can get some lift from a powerhead, but it is very inefficient. A small mag or quietone pump will make your sump work much better than a powerhead and not turn anything into a hurricane. You can control the output from a pump with a ball valve made for use with PVC. Make sure you put it on the "return the water to the tank" line.
Aquascape? I'm a crypt farmer.
It's a fine line between fishing and standing on the shore looking like an idiot.
That IS an aquascape, it's titled "The Vacant Lot".