Use mouse/keyboard repeater/broadcasting.
So when you configure one toon/account, you're doing the same for all of them.

Then any element that is account wide, is the same for all toons.
Anything that is toon specific, hopefully you can save a profile and then load that on another toon.

If you cannot do profiles, you can try copy/paste the relevant stuff in the WTF folder.

And if that doesn't work, then configure a few addons manually.