So basically if Clinton can garner 23% of the White vote in a 4 person race, or even further 25% GA will likely flip?
Assuming the vote for Johnson is large enough (Stein will not be on the ballot in GA), then yes: that could work.
What may be more likely (assuming Johnson doesn't get more than 1% or so) is that she'll need 23% of whites (2008 Obama) + 86% among non-whites (2012 Obama) to be in contention...and even then it's no guarantee.
Unfortunately, I did not put more combinations in the spreadsheet; the combinations that exist among white/non-white levels of support tend to increase/decrease at roughly the same amounts up and down the sheet. So, for instance, there isn't a scenario on there were Clinton gets 23% of whites (2008 Obama) and 86% of non-whites (2012 Obama).
However, that parallel increase/decrease between support scenarios does make it possible to roughly, basically, physically 'average' the distance between two support scenarios up there (remembering that whites are roughly twice as numerous as blacks) to get an idea of where her share of the vote would be. So, for instance, if we take Obama 08 white support and Obama 12 non-white support, and we know that whites are roughly twice as numerous as blacks, then we'd plot that point (twice as close to the relevant white scenario as the non-white scenario) and draw a line over to the white/non-white electorate we're expecting, and:
Somewhere between 49-50% of the vote in that case.