Best depth for a shallow reef? 30"X18"X ?????

I'm building a tank that is 30"X18"x shallow. I'm thinking of going somewhere in the 12" to 15" deep range for a mix of softies, lps, a couple easy SPS and fish and inverts.

What do you think would be the best depth and why? I'd love to here your experiences with shallow tanks?
What lighting are you planning because that affects your choice. For example my frag tank is only 9 inches deep, so it's been hard not to have too much light for LPS. Since you are going mixed reef, I would say the deepest you are comfortable with - 15, 16 inches to give a variety of par values.

This guy has a nice setup:

Currently, I'm planning to use 1 Noopsyche Pro v3 to intentionally have uneven light coverage to have variable par.

Are you suggesting that the difference in depth from say 9" to 16" deep has a big impact on Par. I would not think that 6 inches would have that much impact (but my assumption may be totally incorrect.)

Yes, Danny's Aquarium is stunning. I've watched a few videos about that tank but thank you for sharing.
Are you suggesting that the difference in depth from say 9" to 16" deep has a big impact on Par
I'm suggesting that it limits your ability for coral placement. If you have 300+ par for your SPS, it makes it very hard to get down to 100 par for your LPS and softies when you only have 9 inches of depth.

My frag tank is lit with T5 and I found it very easy to overpower LPS with just 4 bulbs and some accent blue leds. I basically run 2 bulbs most of the day and all 4 for only 2 hours mostly to satisfy the few SPS in the tank.
If lighting was the glitch, I would probably skip the SPS and go with what looks good, is easily to work with, leaves enough space for rock and coral, etc. If I do SPS, I would only do lower light ones like Birdsnest and maybe Montis