Why use @Waterfox ? You can hide:
- tabs, its bar&blur it
- back&forward buttons
- disabled menu items
- url bar icon box
- page action
- bookmarks bar&icons, labels
- sidebar&header, turn off animation
- all icons&tab's
Else:
- turn on/off square app menu panel/item/button/tab/entry field corners, checkbox, monospace font for page/theme, panel/menu transparency
- reduce context/bookmarks menu padding
- center tab title
...and more!