I'm asking because I've read a thread that urges the modders to use as fewer textures as possible so I was curious as per where might I have a limit, regarding texture sizes and quantities.
Well yes, textures are currently (and probably will be for a while) one of the biggest performance drains for any 3D application. For example, load a ship like the Amaterasu in PCS2. Drag it around. Notice how slow it is? Now switch off texture viewing (the button on the top bar) and drag it around again - now there's no lagging.
For fighters, I use between 2 and 5 maps - one with the actual hull texture, one damage texture for debris; invisible, glass and cockpit textures if needed. But you should be able to use the same texture for all lods. Oh, and 1024^2 should be plenty for a fighter.
As for tilemapped ships, make it look good with as little maps as possible, that's all. There are hard-coded limits on what a single model can use, but you'd have to be pretty insane to reach those.