Well.. It is power.. A shuttle us usually battery powered or maybe a fusion reactor .. ( Danube and larger have a small warp core) and they only get up to warp 3? (Or yes.. Plot speed)
So the bigger more powerful the reactor the faster you go or so..
So say voyager has a more compact and powerful reactor than other ships that size
So the bigger more powerful the reactor the faster you go or so..
So say voyager has a more compact and powerful reactor than other ships that size

you." Meaning that you can feel very free with the technology but it can seriously impact the story.