One other question is what is Biden wins some of these states but not others.

Biden is ~99% to win if he wins *any two* of FL, NC and AZ but Trump wins the other one.

But what if he wins just one of the three? https://twitter.com/TrackerDebate/status/1318913887425732609

That starts to depend more on which state we're talking about.

Biden is 88% to win if he wins FL but loses AZ and NC.

Biden is 89% to win if he wins NC but loses AZ and FL.

But only 72% to win if he wins AZ but loses FL and NC.

Getting in the weeds here, but why is winning NC an equally good sign for Biden as winning FL, even though FL has more electoral votes?

Because NC's demographics more closely resemble the Midwest than those other states, so NC might tell us more about PA, etc.