Cruisers were pretty normal cruiser size, but punched far above their weight because the high techness and such.

Capital ships were dramatically larger. They've scaled anywhere from 100km to 1000km long in their past incarnations, so pick a number that makes you comfortable somewhere in that range. Combat power would've increased proportionately. They'd outclass any hyperdread or combination of hyperdreads the galaxy could build.

I'm pretty determined that we will not be encountering those in the RP.