What is ideal depends on your goals, budget, available space and time.
Bigger tends to be better. About the largest production tanks are 6’ in long dimension like the 180 gallon. But even 6’, is cramped for many of the tangs or triggers. For those fish 8’, 10’ or even 12’ is more like it. But those sizes just are not really feasible for most of us.
An aquarium is a trade off of options. A large height looks great but it is hard to reach the bottom of even at 24”.
A nice depth really looks great and makes for good aquascapes. 24 inches is about as big as you see in this dimension in production tanks. But 30”, 36”, or even 48” are really nice. But if you put it against a wall, access can be tough.
The tank you are thinking of sounds good. You might think of 60” or 72” for your long dimension, if you want tangs.