I didn't really use things like Tiled, except for the world map and for things like drawing paths, since C2's tilemap editor is kinda weak. I saved my project as a CAPX and it's 64mb.
I thought of making the tilemaps load from project files, but that's going to make it hard to tell where to place enemies and such.
Also, my stages are made up of multiple tilemaps, because I made the scrolling based on their bounding box sides.
EDIT: My tilemaps are in multiples of 320x240, with a tile size of 16x16.