My bet is that he pulls more Republicans than Dems. Should balance out at the very least. May even hurt Republicans more. I won't consider No Labels a threat either way until they do the necessary and expensive footwork to get onto ballots.
Joe the Better needs to not run. What concerns me about him is that if he does decide not to run, he'll wait until Kamala is the defacto and obvious choice as successor, and we won't get a chance to decide on who the Dem candidate should be.
I don't despise Kamala the way you do, but voters should decide this.