I' m currently building the Italeri Theodore Roosevelt as the George Washington.
While the fit, etc., on the Nimitz class kits is fine, you do need to do a lot of work if you want to make the ship anything more than the 1975 Nimitz with different decals.
Currently, all Nimitz-class ships after Dwight D. Eisenhower CVN 69 through the Harry S. Truman CVN 75 have extensions aft along the upper decks of their islands. Oddly enough, the Nimitz and Ike "lost" those extensions during their refueling and complex overhaul and the "basic" island shape returned to closely resemble their original configuration. The details are much different though. Of course, the Reagan's island is very different. I'm sure that is reflected in the kit.
Having good documentation, doing some scratch building and using a good PE set will make the model work very well, particularly at this scale. I'm using the Gold Medal set which is wonderful. It contains lots of choices, such as the different types of radar masts for making each individual ship.
You'll need better aircraft too as the Italeri ones are just rotten. Fujimi and Sky Wave make very nice 1/700th scale planes and helos.
Mike