I know the tag line says "be a villain or a hero" but honestly it's a gross oversimplification of the paths you'll be able to explore, and all the gray areas in between. Besides, I wouldn't say there's a certain way to best enjoy the game - I'm putting effort in all routes and options and alternatives so that any way you play you get a satisfying experience.
At this point in the demo, anyway, Mordred's not a "hero" or "villain" or anything else but a kid growing up, and it's up to you how you want to shape them.
Also, I'm not quite sure what you mean by "prophecy route"? Mordred, regardless of how you play, is born under an ominous prophecy made by Merlin. That's all routes :) How that actually unfolds, we'll see.