The eZ Platform Features states about eZ multisite and multilanguage capabilities.

The basics multisites is covered in the Multisite documentation page.

The multilanguages, in the Internationalization documentation page.

But I can't find in the documentation no information on how to have different designs for different siteaccesses. In the Design you won't find the "eZ" way to do it and that must be documented.

It's important as well to state the difference of the Base layout for legacy fallback and the multidesign.