Great summary. My answer to the OP would be all of the above.
Amy's performance with Kavanuagh was absolutely commanding. Miles the best of any of our senators. I already thought she was special but then that questioning demonstrated her superior instincts. That is what I'm looking for, more than anything -- charisma and tremendous instincts to battle the Trump/GOP onslaught.
John Kerry had an impressive resume but awful instincts. I remember the howls from my friends in Las Vegas when he went wind surfing late in the campaign. I'm very worried we'll nominate someone like that again, a person who looks great on paper and on offense but has no idea what to do when unfair and preposterous attacks are coming from all directions, placing him/her on defense.
I know that Amy would relax and smile. Her response would be charming and witty. Everything would resemble her Kavanaugh effort. If we nominate someone who thinks claws have to come out, it is the equivalent of raising Trump's approval rating 5 points all by ourselves.
A female in particular really has a difficult balancing act. Frankly I'd prefer a male nominee but other than Beto I don't see anyone who fits what I am looking for. I hosted enough debate watching parties in Las Vegas to understand how difficult it is for a female nominee. Dina Titus ran for Nevada governor in 2006 against Jim Gibbons and made statements that I thought were perfectly tame. But the apolitical types in my living room reacted negatively, especially the females. Titus lost by about 4 points. I always knew that Hillary had almost no margin for error in 2016, because her personality and style resembled Dina Titus. If a female like that is the nominee it needs to be an incredibly favorable scenario nationwide, like Hillary would have had in 2008 and Dina Titus did find in 2008, in a congressional matchup against jackass Jon Porter.
Our voters are mistaking 2020 as an incredibly favorable scenario. I am fully prepared for an overly aggressive mistake in the primaries, like I experienced here with Andrew Gillum against Gwen Graham.
If an overly aggressive mistake is made, then we simply need to get lucky. Trump would need to flub repeatedly and the economy has to be on the downswing. An Amy Klobuchar type expands margin for error instead of retracting it. She could defeat Trump amidst normalcy.