I would be shocked if younger whites in GA were as R as the OP's map indicates. Given Biden won 30% of the GA white vote overall, I would think he won something like 40% of whites under 35. We're much more elastic than our parents and especially grandparents and I would think drove a big part of the shift towards Biden overall. Younger whites are also disproportionately more likely to live in the state's urban areas and in college towns like Athens, where it's pretty clear the white vote is actually majority D. Even here in Forsyth, there's a huge age divide among white voters - most of my white neighbors younger than 40 were pretty split between Biden / Trump while the older white neighbors seemed to be overwhelmingly Trump.
This is what the Fox exit poll has for Whites in Georgia in terms of R vs D.
18-29: 62-34
30-44: 63-35
45-64: 74-25
65+: 71-28
So the Fox exit poll has Trump winning 18-29 whites by 28%, 62-34, the Edison exit poll has him up 60-38, by 22%.
