Mayor Pete is the best overall option IMO, but he will not win. Joe Biden is going to win, but has absolutely no chance at beating Trump (He's a creepy old man with dinosaur politics. Ex- not wanting to legalize marijuana which would be an obviously powerful tool for him to use).
I agree about pete, he would be the most difficult for Trump to attack. What's he going to do, call him a homo?
Petes biggest hurdle is that Black people don't like him. Pete with an Obama endorsement and Booker or Kamala as VP would be very solid - but not much of a chance of that happening unless Biden drops out for some reason. Promising future for 2024 or later though, unless he fucks up in the next few months.