Images in the same folder will be packed into the same texture atlas page image, unless they don't fit, then they will spill over to a new page. Images in different folders will never be packed to the same page images. There is a combine subdirectories setting that causes everything to be packed together, even if in different folders. By using a pack.json file you can have some folders packed to separate atlas pages and others use combine subdirectories.
You could have a page1 folder, as you mentioned. You can name the folders anything you like.
