A single cam V8 can make more power than quad cam V8, if it is tuned that way.
The reason why most newer engines in general are twin cam(4 cyl) or quad cam V8 is to do with VALVES.
The more valves you can get in the chamber the better the emissions and power can be made, two smaller inlet valves delivering a consequently higher port velocity than a single big one will produce more torque, and have better tractability.
With this in mind it is easier to arrange a seperate cam for each set of valves, due to space in the head design.
Of course some engine don't have cams at all, some have aspin valves are so are desmodromic drive, VERY VERY few though, never seen one just read about them.
tabetha