The number of inputs and outputs are dictated by the application, such as is it a high-side / low-side driver, half bridge driver and the number of gates that need driving. The voltage range is dictated by the application and operating environment. It is important to consider ringing, transients, and other stresses that may occur. If the MOSFET or IGBT has already been specified, then match the voltage rating of that part. Otherwise pick a rating at least 1.5 times the maximum operating voltage of the application.