My rule for plagiarism is simple: if you didn't write it yourself, credit the author and link to the source, if possible. If it's a quote, fine. If the main body of the text isn't yours, and you aren't adding commentary or otherwise substantially transforming it, decline payout.
As for spam, you've already met the kind of copy/paste nonsense I downvote most.
I think that is a good rule for plagiarism. I mean citing sources is not that hard lol
Takes like 10 seconds... 🤣