As for what units you want to use, (# LY/hr) would be a more relate-able every day unit of speed; similar to kph or mph which most people use when driving.I don’t think the way we talk about ship design makes sense from a realistic perspective. Starships are traveling at thousands of miles a second, with firing ranges thousands of miles away, and weapons traveling at the speed of light or faster. I don’t think factors like ship size play a large role in targetability. More important is shield power and weapons, and the Galaxy has plenty there. But I mean, it was a huge ship and still one of or the fastest in the fleet at the time it launched. Not because it was small or pointy, but because it had sophisticated engines.
As for firing ranges, according to ST:TNG Technical Manual:
The maximum effective tactical range of ship's phasers is 300,000 kilometers.
For scale reference, that is ~7.4861x the circumference of Earth.
Voyager's Photon Torpedo has a approximate maximum range of 8 million km.
Ship size really only matters in CQB between vessels; once you're outside of that range & ships are specks in the sky, it really doesn't matter how large your ship is because you're not really targeting sub-systems, you're targeting the center mass of the ship.
When you're a speck in the sky in terms of targeting profile & long range combat, STL Acceleration/Deceleration & 3D maneuverability matters alot more along with how fast can you rotate your vessel to make sure you only expose the strong sides of your shield.