Clarification on Disk Image and Configuration

I'd like some insight into the difference between saving a Knoppix configuration and creating a persistent disk image. I only ask because I'd like Knoppix to boot the same way each time, configured how I've specified. I created a persistent image on my USB drive and I do a home=scan at the boot prompt, but it seems this image is updated live, so all the changes I make are saved. I'm trying to avoid this in case I do something I want to reverse, I can reboot Knoppix and its back to the way I want it. Any insight would be greatly appreciated.