A single 3.5 inch floppy will hold only 1.4 mega bytes of information. It takes a lot of floppies and your time changing out the disks. Use one of the other methods. It will save you quite a bit of time and effort. Hard drives will crash.
Viruses can destroy.
Power fluctuations can render a PC to the trash can. But, if you back up your data religiously the amount of unrecoverable data will be, at worst, minimal. A misnomer to be sure. Firewall software does not prevent a fire. However, a good firewall program, setup correctly, does prevent scroundrels from 'breaking' into your PC electronically while you are on line.