Since it's your paper you can pick a ship class for which you can find good readable sources. There are actually a lot of good options and the question of which ship was "most predominant" is kind of nonsensical, since no single type was really.

Maybe a good place to start is reading some stuff from Norman Friedman for the U.S. side and the authors of the Combined Fleet website for the Japanese side.

Prior to September 1 1939, most people thought the Battleship would be the predominant warships in any future war between Japan and the United States. The Imperial Japanese Navy knew the US Navy and the Royal Navy were both much larger, so they designed a battleship that was much bigger. The Japanese completed two of these Yamato class battleships and converted a third into a large aircraft carrier. It would be easy to find books about the Yamato and compare it to the ten modern battleships that the US Navy completed during World War II.
However, battleships were not the predominant type of warship in the Pacific theater of World War II. Even before the war in the Pacific started, the Royal Navy showed how important aircraft carriers were. The Royal Navy sank three Italian battleships in a surprise night-time raid on November 11 1940. They also used carrier aircraft to cripple the German battleship Bismarck.
In the Pacific theater, aircraft carriers were involved in many more battles. In 1942 there were four carrier battles where both sides were evenly matched, using fleets that were small enough that you could do a side by side comparison that is both in depth and short enough for an undergraduate length paper.
You could also compare Japanese and Allied cruisers, or destroyers or submarines. The key is, you should narrow your research down to a specific type of warship. That way, you can give some depth to your research. There were so many warships in both navies, that an attempt to compare them all, would lead to giving each class a one or two sentence description.

One area I might recommend you looking at, which had many active ships on both sides would be the so called "Treaty Crusiers"

Under the Washington and London naval Treaties in the 20's and 30's the fleets of the USN and IJN had very specific restrictions put in place.

A cruiser could not be more than 10k tons, nor mount guns larger than 8in. Light Cruisers were defined then as those with 6.1in or smaller guns. The treaties gave tonnage and number of hull totals for both sides and were followed pretty closely by the US, and RN, less so by the IJN but ships were still a trade off.

Many of these ships then would see service in the waters of Guadalcanal in the 2nd half of 1942. More so than any other theater here is where the two fleets fought the majority of the wars surface actions. I would suggest looking into the classes that fought there.

The Atlanta class, the Pensacola or Northampton, or the New Orleans class which lost 3 members in one night on August 9 off Savo Island.

Against them were IJN crusiers such as the Aoba, Furutaka and Takao classes amongst others.