What you like and what is best for the fish/corals can be two different looks. Try to strike a compromise.
I've been on any number of dives where arches are the predominant feature of the reef. I would agree, however, that they are uncommon in freshwater areas.
On a smaller scale, in the front right of the picture is a 100% natural arch formed by my Montipora Confusa.
As for overall flow - what size tank and how many gph form those powerheads? I see mostly LPS and a few softies, so you should be aiming for someplace in the 40x+ range for in-tank flow. For the LPS it should be at least moderatly turbulent all the time. You can get that by moving the powerheads you have and perhaps adding more. I'd suggest moving the two you have to the back corners, about 1/3 of the way down, and pointing up and in towards the front center. The idea is to have the flow collide on the front glass and spread out from there. The turbulence at the surface will help greatly with oxygenation and the chaotic flow will help prevent the dead spots.
For my 120 SPS dominant DT, I use a pair of Maxspect Gyre 250's on the back glass that max out at 70%, a pair of Koralia 1500gph power heads placed in opposite back corners as I described above, and a 850gph koralia that sits low in back on one side who's only job is to keep flow going behind the rocks. I figure total in tank flow at about 70x. I don't include the return pump (eheim 1262 , maybe 800gph) in the calculations.
hth!