How big should a mobile menu be?
To ensure your menus load at a comfortable size for reading, it's best to design your mobile menus with a page width of 6” or less. As a starting point for designing a digital menu, begin with a page size of 4” x 6.5” and increase the height as needed to fit the content.
Which 3 items are available in the mobile navigation menu?
Customize Navigation Items. You can include Visualforce pages, Lightning pages, and Lightning components. Make sure you've created tabs for those items first.