Based on who has sent back their votes (see link below), there will be about a 1 million vote swing to Biden once mail votes get counted. A lot of counties won't start until late Tuesday night or Wednesday morning (they've announced this). Philly and Pittsburgh should report a bit faster, but won't be done Tuesday night most likely.

Given that WI and MI will take some time to count mail ballots as well (overnight for WI and a couple days for MI), it's very very hard for Trump to get to 270 on the map until those three states are nearly done. My read on this is that if Biden wins some 2+ of FL, GA, NC, OH, and AZ that should count quickly, then the outcome will be pretty clear. On the other hand, there's basically no map for Trump that gets him to 270 without the mail votes being substantially tabulated in some/all of PA, MI, and WI.

So your scenario 1 is nearly impossible for Trump. 2 is possible, but I don't think you'll see it until Wed morning at the earliest and more likely not until Thurs or Fri. That's the danger if Trump declares victory around midnight Tuesday.
[Post edited by CMUHoo at 11/01/2020 3:32PM]