This CSS is a basic proof of concept to turn component options in Composite Products into 'Cards':
To try this out on your site, be sure to set the 'Stacked' and 'Before tabs' layout options on your composite product:
Once you've set up a Composite Product with those layout options, you can add the CSS to the Additional CSS area in your Customizer.
Note that this should be considered a proof of concept and a starting point, not production-ready CSS. For instance, this has no awareness of mobile device sizes.