Well -- SD! isn't open source, Jude.
Anyway, if you properly partition the Iomega drive as "GUID" before copying to it, and you copy directly with "Backup - all files" and "Erase, then copy" or "Smart Update", it should be bootable on an Intel Mac.
If you want to keep other files there, you should partition it into more than one volume, one for the backup and one for the other files.
And, yes, you should make a full backup. It's a lot easier to recover from when you have a full backup -- the small cost in disk space (the system, after all, is only about 4GB) is more than compensated for by the hours of time you save when recovering.