So just glancing around - for the Democratic primary alone - it appears there are at least 75,000 votes outstanding in Fulton/Dekalb combined, and potentially 50,000 or more in Gwinnett/Cobb.
On top of that, there are still plenty of counties where mail ballots are obviously not (fully) counted. Forsyth is one example: there should be no fewer than 10,000 D ballots there (maybe closer to 15-20k), yet there are only around 6,000 D presently.
Floyd is another example: only around 1,500 D presently, when it will likely end up in the 4k range.
Several thousand D ballots at minimum haven't been counted in Bibb based on its turnout relative to Muscogee and Richmond.
My estimates based on comparing votes counted by vote type and number of absentees reported as returned:
Fulton has around 20k left, DeKalb maybe around 75k.
Gwinnett around 50k, Cobb 35k.
Forsyth has yet to report any mail-in absentees, around 9k or to there.
Bibb hasn't even included any absentees (mail-in or early in person) in their totals, should be around 17k votes there.