I only use one catalogue per release, and I have my images within the Pictures folder and my Lightroom catalogues, etc. also within that folder (all within subfolders, etc.) Older images are archived on an external drive, also within a Pictures folder. By backing up that one folder (and subfolders), I back up my images, my catalogue(s, including older versions), my presets, keywords, previews and pretty much everything associated with LR. The actual program and system presets, etc. are stored in different locations.