There are some states that will portend the presidential election outcome. Winning one or two of certain states is almost a sure-fire guarantee of victory for either candidate.
If Biden is declared the winner in any of the toss up states of Arizona, Wisconsin or North Carolina he is probably the next president. Trump's almost certainly needs to win all those states to be re-elected. If Biden wins Florida he has been elected.
If Biden is declared the winner in any of the electorally-rich Republican leaning states of Ohio, Georgia or Texas he is certainly the winner. Biden winning Iowa with its six electoral votes helps his cause greatly but might not secure a Biden win.
If Trump is declared the winner in any of the Democratic leaning states of Michigan or Pennsylvania that would be major upset and he is very likely re-elected. Trump could win Minnesota, New Hampshire or Nevada and still lose the election, but it's no certainty.
In all but two of the above-mentioned states, any voter can vote absentee. In New Hampshire an excuse is required to vote absentee. However concerns about coronavirus is considered a legitimate excuse in the Granite State. In Texas an excuse to vote absentee is required.