Although it does seem odd at first that the vast majority of the information about this comes from Fox News, it is confirmed to be true to some extent. When Biden's former White House Press Secretary Karine Jean-Pierre was asked about the notecards, she said, "It is entirely normal for a president to be briefed on reporters who will be asking questions at a press conference, and issues we expect they might ask about. We do not have specific questions in advance, that's not something that we do..." This clip of an interview was posted on CNN's official YouTube page and is referenced in talks about the notecards. Sadly however, I could not find the raw footage of this interview.
I was able to find the original Fox News article on these incidents which was the main source of information for articles posted by outlets such as the New York Post and KOMO News. It's important to remember, however, that these news outlets are considered to be more conservative leaning, so some aspects of these articles may be dramatized.
I find it incredibly odd that (with the soul exception of CNN), no moderate or democratic leaning news source has posted anything about this. If it weren't for the interview with Karine Jean-Pierre, I would have absolutely thought this was false, but due to her confirmation of the cards existence, it does seem to be true to the extent of interview questions. Most of what has been written on the subject does seem to be exaggerated to imply a lack of cognitive function from the former president. Although this topic is still heavily debated to this day, Biden's physician determined a cognitive test to be unnecessary during his time as president.
(Side Note): Although Karine Jean-Pierre was previously in a White House elected position, she does not currently have a publicly available email, so sadly I cannot ask her to comment further to answer your other references to notecards with information for democratic representatives.
Karine Jean-Pierre's Confirmation (CNN): https://www.youtube.com/watch?v=IKOusB4FVjU
Original Article from Fox News: https://www.foxnews.com/politics/exclusive-unearthed-biden-note-cards-reveal-he-had-bios-photo-reminders-hillary-clinton-schumer