Height of the tank doesn't really help puffers much, its more about the footprint...
So at 30" wide, i'm going to guess its also 30" front to back making it a somewhat square?
With that size tank, you are pretty much going to have to stick with either the mid-size lurker species such as Palembang Puffers / Arrow Head puffers, or some of the smaller active species such as South American Puffers / C.irrubessco / Dwarf Puffers etc...