The spots are spaced out enough on the city map that I don't think that anyone would object however each person decides to map their patch.

Layers is a feature of CC3 being basically a CAD program.

Normally in a CAD program layers are used to group items by what they are, so for example you could hide all the doors in a building or the nuts and bolts in an engine.

Back before sheets were added (giving Photoshop type "layers") you had to sort out drawing order for the entire drawing yourself, which really meant pre-planning and adding entities in the right order or doing lots of select by layer & move in front/behind.

Although it's a little confusing for new users used to graphics editors to get used to CC3 with it's CAD naming, it is still nice to have both sheets and layers, especially with GM Only and Secrets layers, or just for turning off all the doors before exporting for virtual tabletop use.