Without a map in front of me, I cannot regale you with how far it is from Florence to Holly Hill, but Bub Sweatman's in Holly Hill is a likely destination for you. Remember it's got limited hours, as do most of the pig-pickin' places in that area. (There doubtless are good places in and around Florence/Darlington/Hartsville, but I am ignorant of them.)
Up the road from there, I-95 passes through Weldon, North Carolina. Right beside the Interstate (but predating it) on U. S. 158 is Ralph's Bar-B-Q, and it is a goodie. They sport that vinegar sauce that you pour over the meat, plus they have a plethora of great sides on their buffet.
Farther on up the road (to quote the great Bobby "Blue" Bland), King's Barbecue in Petersburg, Virginia is likely the farthest-north outpost of real, live, non-corporate, authentic barbecue you are apt to find. It's not hard to get to: it's located on U. S. 460 Business on the far west side of town. Everyone knows how to get there.
Let us know what you find.
As If On 'Cue, Ort. Carlton in Athens, Georgia.