The cardverse AU is based off of Himaruya’s artwork of some of the characters dressed as Kings, Queens, Jacks, etc. and was included with the release of one of his art books. The actual AU has nothing to do with legit playing cards.

I’m aware. You still have to have a general understanding of the meaning and symbolism of cards to understand each Kingdom’s position, no? 

That’s what I had initially meant. I literally have no knowledge of cards at all so that’s why I didn’t think I was the best person to explain it since I’ve never been into the AU + directed them to a tropes website that would.