How does one identify a type of ballast?
Modern retrofits do not use a ballast at all like this. Most have universal drivers, they can run on 100-277 VAC 50Hz or 60Hz. Here is another example. Things to think about, the color of light 5000K will be a very white closer to sunlight, 3000K is more yellow orange. With the same lumens I think the 5000K and higher wavelength lights look brighter with the same lumen count. 
The type of lamp is the part that gobbles up the energy. florescent are more efficient than incandescent largely because they do not generate large amounts of heat to create light. florescent lights work on a gas plasma. LED's work with a diode junction. As technology has evolved the amount of light a LED can produce per watt of energy consumed has increased many times. There are many types of Ballast's and the type of Lamp you have will determine the type. The majority of homes have 4' T8 lamps (1" in diameter tube) some are T12 1-1/2" tube in both 4' &amp; 8'. some of the retro kits have a strip of lights screwed to the fixture some have tubes similar to the florescent. Investigate a bit more and you will find there are hundreds of options out there and most don't use the ballast.