I think Shapiro is too flashy and has some downsides to him. He would be a good nominee but it's too strong for a VP. Might be better to go for someone more milquetoast like Kelly or Beshear which is what I expect to happen.
Not sure about Walz, maybe he helps with Wisconsin a little but also has some downsides (looks like a Boomer, and will be bombarded with George Floyd stuff).