Historically, Communist leaders have typically preferred dealing with hardheaded American businessmen and right-wing politicians over left-leaning idealists and intellectuals, because they found the former group to be more predictable, more willing to reach mutually beneficial agreements, and less annoying over human rights issues. As a result, a fairly substantial number of people in China looked forward to Donald Trump’s presidency; for all of his obvious foibles, here was a man who enjoyed doing deals, and could be easily manipulated.
That was then, and this is now. In practice, the Chinese have found that Trump is completely capricious, largely because he himself has no idea what he wants. Hence, the long and pointless trade war, and the danger of worse to come.
Would the Chinese rather have Warren or Biden? It’s a mixed bag. Trump is discrediting American leadership with our allies and making their system look more attractive to the rest of the world. In addition, Warren in particular would undoubtedly make human rights a much bigger irritant in our bilateral relations. On the other hand, the trade war is undoubtedly hurting their economy, and a Democrat might put an end to it. The likelihood of stumbling blindly into World War III would also be much lower.
My guess is that they choose not to choose, and will remain neutral, both in private and in public. That’s what I would do in their position.