I completely forgot about the era of airships! You're right, those things were monsters.I think this perception of size also depends on whether you grew up with the massive rigid airships pre-WW1...
Ships like the USS Macon were 239m in length so it would've been a heck of a sight to see back then.
I tend to imagine that the catamarans were largely uninhabitable, and I definitely think of the secondary hull I created for this NX re-imagining as having a lot of machinery and storage taking up that extra volume. But it would be a fascinating idea having a show set on a ship as cramped as a pre-WW2 submarine, for example. Lots of psychological stresses to write about in a spacecraft like that! As you say, it would've been a real pain to film - every wall would have to be really easily removable.Honestly I always thought the NX class was still too big for Earth’s first true starship. While much shorter, she’s not far off the volume of the Constitution-class due to all those convex rounded shapes… in fact due to the NX nacelles being much smaller than the Constitution nacelles the NX actually has a larger habitable volume! And that’s before the secondary hull refit! The NX should have been much more cramped and submarine-like. Probably would have made the sets harder to film in though.