Ok I have a project in mind, its somewhat ambitious but not so much. I'll explain.

I want to create a Camelot world, not a total conversion just a new world that players can explore and follow the story of merlin and king arthur the knights of the round table and all the jazz... with most of the assets being NPC's/Items/buildings being edited/used from the vanilla version. The issue i'm having is I am having trouble picking a place to start.

I know I'm gonna need a new world, I know i'm going to have to set up a new region, I know the place names, the different terrain's i want/need he location of where they will be placed, but the thing is when I start to edit my terrain i get stuck. Not cause I don't know how to use the editor but because my terrain turns out to look like crap, and its hard to focus on one area when the editor keeps generating new cells, i know i can shut it off and I have but then its also hard to tell which cell is where and which one i'm working on. I have a vision of the completed terrain in my mind it looks amazing but I just can't seem to put it to paper so to speak.. Mainly cause each part of my map will have different cells and I think it would be easier to create them separate and put them together later, but i'm not sure how to do this or if this is even possible

Is there any tips or guidance you guys can give me to help me edit/focus on one part without it getting too messy. Or am I approaching the whole thing wrong, should i lay out the paths/textures of the important things first.. how should i approach this?