Welcome to the addiction!
What are the dimensions of your tank? A standard 55-gallon is 48x12x21" but yours looks wider than 12".
Fwiw, sumps do not have to be noisy. My system is definitely quieter than even the smallest air pump. There isn't even a whisper from it. I'd strongly recommend a sump because you can buy a much better skimmer for the sump for a much better price than hang on skimmers. It's tough to find a good hang on skimmer used. Don't bother with Remora skimmers or CPR Bakpak or a bunch of other terrible skimmers. The Deltec hang on is the best hang on you can buy and the Bubble Magus is good too. Those are the ones most readily available that I've seen/used. Either run the tank skimmerless or buy one that is really good. A crappy skimmer isn't worth the cardboard it's packed in, and honestly you're better of spending that money on salt for bigger water changes if that's the case!
Fwiw, Monti Caps are SPS too, just like birdnests. Both are relatively easy to take care of provided you can keep nitrate and phosphate low enough.
Don't be scared of live rock. I've been in this hobby over 20 years and I only use live rock on my own tanks. I run a tank maintenance company and some of my clients by dry rock. It takes sooo long for the tank to age. Those tanks always lose corals in the beginning where live rock tanks are easier to take care of at the beginning. Some dry rock is very heavy and not very porous which makes poor live rock. Good live (or dry) rock feels lighter than you would expect for the size of it.
Also, I never both with buying "live" sand. It's really not that live, and if you use live rock the "dead" sand will become live in no time. The same can't be said for dry rock though. It takes about a year for dry rock to become as live as live rock.