Symmetry Theme - Change mega menu style and alignment

[clhbst]

Hello all,

I'm editing a website for a client that is using Symmetry Theme and I want to change the style of some elements in my mega menu.

The main menu elements change style when they contain subcategories, and those that do not contain subcategories remain the same and the layout is messy : 

Ideally I would like that when a mega menu opens :

- All Categories have the same style even if they don't contain SubCategories (here in the image the categories are : Miroirs, Vases, Coupes décoratives, Fleurs séchés, Plateaux, Bougies, Cache pots, etc.)

- The menu elements to be aligned

Does anyone know how I can achieve that ?