Sorry for the late reply. Generally try to stay out of the details for warp stuff b/c most stories aren't based on those kinds of details, but I think I can answer the essence of your questions. Warpdrives require a lot of power, which is usually taken care of by either a fission or fusion reactor. Hyperspace travel does not have the same power requirements, so some of the smaller ships would spend the majority of their transit time leaving gravity wells and then have very brief FTL transit times, or use some kind of warp-based ferry system or a relatively short-range wormhole-based gate system. As a general rule the mass of the drive wouldn't have to be too big depending on ship size b/c the capabilities of the drive system would increase exponentially as size increased, as opposed to increasing in a linear fashion, but as I'm sure you remember from the document, there is a size limit to the warp bubble. Ship geometry is not an issue.