is there any sort of shortcut when it comes to outlining a map and all of its bonuses & territories in inkscape with the bezier pen? perhaps importing a .png with transparent background?

That's what I do - import (or even just copy/paste) an image into it and make it semi-transparent.

in doing so, you don't need to outline with the bezier pen? correct?

Not necessarily. You can use the pencil tool and simplify with ctrl+L. Or you can just draw straight lines.