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.

While CC3+ itself allows for almost infinite scaling, the symbols and fills themselves are still ordinary raster images (To get the most out of the infinite scaling, you would need to use vector artwork instead of raster, but generally that's not as pretty, and while they scales indefinitely so you avoid pixelation, they aren't detailed enough to really look good when enlarged too much). The raster images provided in much higher quality than you would ever normally need, thus allowing you to export the map at quite a high resolution, but there are limits. Try opening up one of the .png images (you'll want top open up the _VH version of the file) from CC3+'s symbol folder in your favorite image editor, and zoom into it, and you'll notice that you can make it quite big before pixelation becomes an issue.

No. The pixelation is a limit of the resolution of the artwork, so the only thing that really affects that is how large (physical size) you make the final output, there are no way to cheat in CC3+ to affect this, it can't make the images better than they are.