I tried to rough this out in paint to make it easier for discussions sake.
As you can see in the top half it looks similar to the photo you've provided. The issues have been addressed by others but basically it has a few problems (or sub-optimal choices at least) and they've been pointed out but I'm including them here for posterity. For starters, the emergency drain needs to be higher obviously, and that's to make it so it only functions in the event of an emergency. Secondly, as
@Shores805 pointed out the main and secondary drains should be higher. Basically your photo looks like there is a 3+ inch drop from where the weir notches begin and your main drain is. Depending on the flow of your tank, this could potentially cause issues by A) being much louder due to the aquarium sending water crashing down to the overflow, and B) increased flow/crashing will likely cause bubbles in the overflow section which will cause your siphon to run sub-optimally and potentially noisily.
The bottom half of the photo above basically shows a better layout for your drain pipes. The main/full siphon drain pipe should be lower than the secondary to make life easier in my experience. However, the water level will naturally be somewhere between the main and the secondary height due to the gate valve adjustments to get that fine tune between the two lines. Ideally, you want this water level to be just slightly under the weir so that when water is pushed into the overflow it will effectively be silent. Imagine holding a cup in your sink and tilting it to pour water out versus holding that same cup above your head and slowly pouring it.
This will significantly quiet the overflow. The emergency pipe should be raise to be just slightly above the weir height (or water level in the aquarium when enough flow is pushing water back into the overflow). This is to make it so that your emergency line is/can only activate when the water in the overflow has risen enough to the point that it is at equilibrium with the water in the display tank. By doing so you will still have the ability to prevent flooding but it will also prevent the occasional sucking/slurping you might hear if you have wave makers in the display that push water into the overflow at varying speeds/amounts.
On that note, I'd get rid of the basket/prefilter whatever you have on the emergency drain. It's needlessly redundant and you want that flow as unobstructed as possible. If you're worried about three different levels of failure due to a snail or something I think an overflow lid would be a better deterrent.
