Same length/width, but much thinner at just about an inch. The mounting points can be moved actually, the slide along in a T-slot so you can position them as you please.
They draw air up, not down.
Also, many many reefers do this on purpose to cool the tank- moving air aides in evaporation, which cools the system through a process known as evaporative cooling.
Unlike other lights with similar fan designs, the air at no point goes inside the light, the fan lies in a hole that draws air up through the heatsink fins on top, which helps the heat dissipate at that point. The fans are temperature controlled and the lights stayed warm to the touch with all channels at 100% for 3 days straight.
So no salt air makes it near any components/internals, and the light has a durable aluminum case that will not corrode, so as long as you clean the fins every few months it will cool the LEDs very efficiently.
Neither actually, you would be best served with 2 32s, though any of those options will work, 2 32s will give you the most light for the lowest price.