Theme Customizer Custom Font Controls

Hi, I'm looking to implement custom font controls exactly like:

This is something implemented in another premium theme (which isn't available to purchase - I've tried). These are non-standard controls and look like they've been custom built.

Issues I'm struggling with:
- Inner accordion like UI for different fonts
- Styling the custom controls so that Font, size, style, color are in a compact design
- Font preview in drop down (ie. best way to load Google fonts for this and efficient implementation for lots fonts)
- Turning into a single control object, multiple or a function (which is best?)

Any help in these areas would be much appreciated - Thanks