There is no universal standard. Tarot is intuitive, and that is why you will find conflicting answers, because it is based on the individual reader. For one reader, it’s the 5 of wands that represents this particular demon, and for another it is the 8 of wands. For still another, it could be the 6 of swords.
The trap most people fall into is thinking that whatever card their intuition points out to them, is the only possible card that can represent the spirit in question, and that is rarely the case.
The best way to understand how spirits are attributed to certain cards is to let your own deck of cards teach you. What you will learn is what will be correct for you.