How to Rid of "Favorites" and "Smart Mailboxes"?

For Favorites, expand the heading and right click on each one to remove any present. They'll all be gone, but you cannot remove the heading itself.

Repeat for Smart Mailboxes. Under mine, the only sub heading was Today. Once I removed that, the Smart Mailboxes heading also went away.

Refer to image below.

This will only Hide them but Not Remove the mail boxes

That's part of mail. Just do not use if they have no value.