So is this a true role playing thing then or more of a MMORPG ? If its RPG then using a VTT would be a good way to go and therefore a 2D map with top down icons. Its quite extreme to go 3D for RPG. If you do then the res of the terrain would be very low at character scale where the action would be. Even a very very high res terrain would be a few hundred feet if not more for the whole land of Arda. Also, if doing this in 3D, what would you use for the towns and cities ? When 2D you have the maps for them from various places.