What types of documentation are other banks providing when a customer asks for it in connection with a decision on a claim??

You give them whatever you used to make your decision. Otherwise, I guess I do not understand your question.

If we used their account history we are supplying statements, if it is a merchant dispute, we have receipts, contracts, agreements, so I was wondering what other bank send specifically. The CFPB challenges everything so I am asking for opinions on what is being sent to customers.

If you relied on it to make your decision you must provide copies in an "understandable form". I don't see it as being open to opinions. The documents will most likely vary with each investigation so whatever was used in a specific case will be what you provide.