OP wrote:
"Do you need to choose "ignore ownership" (under sharing and permissions) everytime you plug in a cloned drive from either CarbonCopyCloner or SuperDuper into a different Mac?"
If you DON'T do this, you -may- run into permissions problems copying or opening files.
The reason for doing it is this:
When you set the "ignore ownership" checkmark, you can now copy anything (or almost anything) into the account you're using. When you do this the "ownership" of the copied files are now attributed to that account, and you shouldn't see any permissions problems when opening the copied files.
So, yes, I consider it a necessary step to take anytime you connect a drive (that fell under the ownership of one account) to ANOTHER Mac that has a different account. This takes care of permissions issues before they start...