1.
--def exec is like running shell commands.
e.g.
echo {n} will result in commands such as
echo Avatar to be executed.
You can do
cp commands, but that'll give you a flat file structure and it won't create folders as necessary. Try doing it manually from bash and you will find that it's not quite as straight-forward as it might seem at first.
2.
The mirror examples are indeed showing how to mirror a master file structure to a different file structure using hardlinks using existing xattr metadata. It'll check all files, but since it'll only use local xattr metdata it'll be near instant.

Once you have a filebot-mirror script that you can call from bash, then you can also have filebot call it via
--def exec. That makes things easy to test and maintain.
