The Meanwell ELN-60-48D model is dimmed with a potentiometer and a 10 volt power supply. The -48P model requires a PWM controller to dim it. The P model is used with electronic dimming circuits, like a computer or a Arduino device. For the D model, you can use the dimming kit that RapidLED sells, or just buy the appropriate potentiometer and 10 volt source.
I expect that that layout would give pretty uniform light over the whole substrate. However you light the tank, any hardscape that extends up near the waterline is likely to grow BBA. You just resign yourself to weekly cleaning of the hardscape to kill and remove it.