I'm not particularily a map maker either (I do art and a little graphic design), though I like maps. And I have a Cintiq 21UX too, I love it.
If you are drawing small maps for the encounters, then doing the map based off the inch grid squares helps. I've gridded out cardstock and sketched out my preliminary maps and monster locations that way before.
For the larger map, I don't think the style of the map matters so much as that the geography fits with the general region you are roleplaying in. Depending on how large the campaign is or the needs of the group, you might want more than one map, or a map that serves a dual purpose. (Like geography + battle, or geography + treasure).
For example I once designed a campaign set on/around the Lake of Steam. Because there were a lot of forests, I got lazy and bought a forest pack so I could pull out new, random forest maps as needed. Then, I flipped over the cards and drew my encounter maps on the back for different places I needed elsewhere in various cities. My large map of the region was mostly focused on cutting out extraneous detail from the Forgotten Realms Atlas while highlighting points of interest.
Terrain that ties in with game play (tactically, magically, or otherwise) may be a factor. There was a map I saw recently at PAX, 13th Age, that took the concept of terrain affected over the passage of time, and by the very creatures in the world, to a level I hadn't seen before as well.
If you start with the simpler/functional elements first, then you can iterate the map into more elaborate designs as it comes together if you really want the wow factor