Change Popular Categories to Featured Categories or add a line in Supreme Dir

Hi. I’ve done some changes to Supreme Directory and i’m going very deep in using the theme.
Changes are few but oriented to make this child theme useful for a live directory. Based on 5 years of use of a live one with success (with a very old theme).

So i’ve noticed three thing:
1) if we can add a second line of popular category on mobile (smartphone and tablet) and on desktop version the final result is very good and the “splash page” “home page” is really more complete
Why two lines? Because using 5 in a row the result is not optimal on mobile. But only three are really a very small portion of a complete live site.

2) It’s possible to transform the automatically filled “popular categories” with a featured category option.
To understand: popular categories are not the more commercial one. And in a city guide is better to have the chance to put the categories that drives more economically useful traffic. If other categories are popular people simply search them without any spin by site administrator. So i must point attention on less visible but more “monetizable” one.
It’s possible to transform popular categories, or add a line with featured. (better the first option).

3) Why in popular categories isn’t possible to put events categories… so point (2) is useful to resolve this…

Can we do all modifies only with css and little modifies on php?
What files we must check to understand how to do it in the more efficient way.

Thank you
GP