Re ships, I thought you were asking for the name of the largest hull size, but maybe you want to know the name of the built-in design(s) for the huge hulls. I'm afraid I can't help you there, other than to say that if you're not designing your own ships, you should start doing so. There are many threads around here about ship design and why you should do your own.
Twilight of the Arnor is the second GalCiv2 expansion pack. The most common shorthand around here is DL (original game), DA (first pack), and TA (second pack, also pretty often called ToA or TofA).
I should note that TA includes a ship auto-design feature (the original built-in ships were just a hard-coded library of designs). It changes how things work, and might still include a miniaturization-related bug that means it can build better ships than you can. I've never messed with it, so I can't say much other than I've noticed talk on the forums about it.
If you don't already know about it, using a good search engine and adding site:forums.galciv2.com to the end of what you type in the search box. Your search results will be limited to hits here at the forum.
