If the cards are that different, I would keep them as separate files.

In most cases, there is no similarity between them other than colours, font sizes and fonts.

As switching to a different card means a reload (I guess)

The cards are all displayed at the same time. One after the next. The current system is designed to be viewed on mobile and has a very constrained width on desktop so they appear one below the previous one. The refactored version may make use of the width of a desktop and display the cards in columns but, as they are all different heights, that won't be trivial.