You also need to consider things such as the technology and automation on capital ships. It's not just about physical size. As well as things like passengers and Marines.
I'd think even the largest warships in Discovery could operate on a skeleton crew (minus marines, docking crew, etc) of a few dozen people. Computerization and all.
So, I'd consider there'd be two or three shifts worth of main crew (bunk rotations and all), a bunch of technicians and damage control teams. Dock crew and pilots (if applicable), marines, passengers, and robots.
I'd think that Kusari ships would have a leaner crew size ones due to high-tech usage of optronics (Kishiro), while Gallic and Rheinland vessels' design philosophy reflects on a larger size. Outcast and Corsair caps would probably have huge crew sizes to compensate for lower technology to work with, as would IMG due to the needs of a lot of science and mining staff. Liberty/Bretonia/Colonials would probably be on the lower end of crew needs.
It'd probably range from Zero (AIs) to One (Tridente) to a few tens of thousands (for a Juggernaut, most of that being population) at the extremes.
