SC whites are about 7-8 points (margin-wise) more Democratic than GA whites. Democratic support collapsed in SC in '16 due to low black turnout (particularly in Southern rural areas; the same phenomenon we saw in MS; given the 2 states are a combination of two blackest-rural states in the country, not too surprising).
Only countervailing issue is that SC is generally becoming whiter (or at least less black), but the whites moving in are disproportionately college-educated, so at worst it is probably a wash.
I'm surprised SC whites are more Dem than Georgia ones given Georgia has a bigger urban (not just suburban) population and more transplants from the liberal Northeast or California rather than Midwestern retirees. Also isn't South Carolina one of the very few states that are getting whiter? Seems to be the reversal of the Great Migration hasn't affected SC as much?
This taps into my "latitude" and "coastal" theories, though they are not the root explanations for why. Basically, the further north whites are, the more Democratic they are. If you look at SC, it doesn't look any further north as a whole than GA, except that the middle half of the state is largely black and rural. You have large concentrations of whites in the northern-most portions of SC voting similarly/slightly above how whites in North GA do in terms of D vote share, and you also have a large concentration of whites along the coast ("more moderate weather climate means more moderate political climate").
I did mention in my OP how SC is getting whiter (or at least less black), but the flow of whites to the state are increasingly not as hostile to Ds given trends along educational lines (and the non-black, non-white flow has largely been insignificant until now).
