Visibility of any element can be set here:
http://vincent.polenordstudio.fr/snap/ykjbd.jpg
So you can hide certain elements for certains breakpoints.
You can decide to hide a full navbar for devices and have a second navbar for devices, that you hide for desktop. I often have 2 differents navs, because I consider that a nav that hides behind a hamburger menu should be banned (yeah like in the law, with prison sentences 
) (I swear I really hate hamburger menus).