I've been in the market research business for many years and I don't put any credence at all in these daily polls. The one I follow most closely is the Gallup tracker. They have used the same sampling and methodology throughout so at least the trends are meaningful.
I think this election is completely different than 2016 because of Trump's incumbency. In 2016 we didn't really have any idea what a Trump presidency would really look like day-to-day. Now we all know exactly what to expect the next 4 years if he wins and people will vote accordingly. This election is 100% a referendum on Trump. Biden is essentially irrelevant.
I think there will be record turnout. Even in states where the EC is a foregone conclusion the Congressional and Senate races will still have a big impact, especially in a second Trump term.