Agreed. I don't have as much of an issue with the traps as the others. I don't have a trap between my first two sections and only an over under between section 2 and 3. I have no issues with bubbles. The size is great, I have a 40 gallon because that is what I had on hand to build the sump with bigger would have been even nicer. You aren't going to have it full, maybe 2/3s at most. Like silverado said the skimmer needs to be in only 6-8" of water depending on the model you choose. I have mine elevated on a pile of egg crate because the water level is too high. You don't want a lot of height you need to be able to take things in and out of it easily. That is the worst having a too tall sump that you just can't easily clean or work in. One of the great things about a sump is that you can hide a lot of equipment in it.
In your pics above you show a canister filter/skimmer combo. I would get rid of that and get a good quality in sump skimmer. Bulk Reef Supply has a lot of videos on their web site that have a lot of basic info as well as how to choose and use various pieces of equiptment. You can go very complex or simple. I like the simple method. The sump filled with macro algae and maybe rock rubble will be a big part of your filtration system. The skimmer will help remove organics from the tank and your live rock will be the biofiltration. Once everything is up and going for a while it will run very smoothly with little needed from you other than water changes. Granted this takes several months if not more to get to this point but it is great when you get there.
While you are planning the display tank I'd start thinking about a quarantine system as well. You will want to quarantine all your fish for at least 30 days.
