Turnout and getting the votes to count will be the key.
As for comparing this year to 2016--far more Democratic presence for federal and state offices in metro Atlanta (city, suburbs, and exurbs). You can even go to Hall County (73% vote for Trump) and see a few Biden signs in subdivisions.
But rural north Georgia has a sea of Trump and Perdue/Collins signs everywhere.
Does this indicate that Trump/Collins are underrepresented in polls?
It doesn't need to be a big underrepresentation for both Trump and Collins to win by a small margin.