Custom Theme Customizer font controls

I found this preview of a theme (which isn’t available to purchase) and I’m trying to model the custom font controls for Theme Customizer they have built. Here’s a video:

Issues I have come across:

-Where to add CSS to style the custom controls

-Implementing the animated accordion

-Font preview in drop down boxes

-Turning 4 settings drop down into a single control or should I just have a code block for each font

Any code help would be great as I’m still a bit new to php/js in WordPress.