Both Windows and MacOS read and write FAT. There's little reason to use something else. If you're going to storing disk images on the disk, then the file system doesn't see the information that you're backing-up in the images. This will limit the size of your disk image files (Ghost breaks them up automatically) and what names you can use, but that's relatively minor.
I use Symantec Ghost to make images of Windows PCs. There are other products, however. Be wary of any system which supposedly can image a disk while you're using it; it's simply not possible to get a static image.
Concerning optical disks... consider that hard drives are orders of magnitude more complicated and, therefore, far more likely to fail. You can expect optical media to last from 20 to 100 years; you might be lucky if a harddrive goes for five. Don't confuse your personal experience with the reality of the world at large. You're several times more likely to die while in a car than while in an airplane, but nearly all people place driving as the safer way to travel.
I would suggest making your regular images to your external drive, and then running one of the backups a couple times a year to optical disk. It's time consuming, but the reliability and ability to keep archives is invaluble.