I like the idea of a "functionnal" map, and I'd go this way if I were you. Not least because it will be easier to draw and use in your campaign:
One important thing to consider when mapping for GMastering (and in other cases too...) is to think how your players have access to the map information. In this case, I think a beautiful, very detailed map is less likely than an old scrap of parchment passed down through the generations to your sturdy Dwarf, showing the then-important places, even perhaps annotated by an old ancestor. That way you can introduce easily the map, and, more importantly in my opinion, filter the information you want your players to have --- and you can still have a rough sketch for yourself with all information. The player's map could even, if you fell a bit sadistic (I know I am), include outdated information...

As for the style, I guess either a really crude handdrawn map (drawn by said ancestor), or an "official" map, with straight lines and official builidings indicated (and some annotations by the ancestor about more specific places).

Just some ideas here, not sure if it can be helpful...

Good luck with your project though!