Election results are math-based, and most people don't like solving math problems. So, very few people are doing all of the calculations that go into who wins and who loses as the count goes on. Instead, they depend on others to do that.
I expect the networks this year to take longer to announce "winners" in each state. However, they will do that announcing when their statistical folks say there is a clear winner. It's all about statistics. When looking at ballots that have not yet been counted, the statisticians look at how that has worked out in previous elections. Most often, the remaining ballots are generally close in percentages to the ballots that have already been counted, so predictions get made about who the winner is.
This year, with a heavy early voting and mail-in or dropped off ballot numbers, the states that count those ballots on election day, like my state of Minnesota, are going to provide clues that can be projected onto states that don't count those ballots on election day. Statistical trends are going to be weighed in predicting results for states that don't count those ballots until after election day.
Where races are very close, of course, it's tricky, and most networks, I'm sure, are going to not call those elections until later. So, there will be some states that don't get announced on Election night. How meaningful that will be depends on how the electoral count looks, based on states that have a more complete count on election day.
Trump, of course, will cry foul if Biden is declared the winner on election day. My hope is that the Electoral College count shows a clear winner on Election day.