Now added to the atlas. Thanks Quenten.

Now in the atlas. Thanks for contributing.

Maps are now in the atlas. Thanks.

Map is now in the atlas. Thanks for the contribution

The amount of detail really depends on how dens you want your printouts to be. Generally, a normal map is normally more than dense enough for multiple sheets, like 1x2 or even 2x2, but when planning for 3x5, then yea, you'll probably want to include some more details, although probably not 15 times as much. Be a bit careful though, the more detail, the longer it will take you to make the map (and the higher the chance you will feel burned out during the process)

For symbol size, that depends on the type of map you are making. For dungeon/city maps, the scale should be 1 no matter the size of the map. But for an overland map of this print size, I might be tempted to set the symbol scale to half the default value (The default value varies with map size, but you can see and set it from :CC2PRESETS:)

I would probably make a few very simple test maps and then print them to pdf as JimP describes just to see if you are happy with the scale. You could even start out with one of the existing example maps and just see how it turns out when you tile them like you want.