Best route from north FL to north side of SMNP?

Depends on how much time you want to spend on I-75, and do you mind going thru Atlanta? Fastest would be US-319 to Tifton, I-75 up from there. US-27 up to Columbus, I-185/85/75 works good also. We reverse this going south to Quincy FL every year. US-27 up to Rome GA will miss Atlanta. There if you want you can pick up US-411 and take it To Maryville TN. Or GA-53 to I-75 at Calhoun GA.

Tallahassee to Adele Ga. I-75 to Macon - then 129 up to I-85

Albany then Columbus then the above if you are east of Tallahassee.

US 27 to GA 146 (Cloud Springs Road) just north of Ft Oglethorpe. Take GA 146 east back to I-75 to I-40.

75 to 40..... very little "Mountain" driving. More of a gradual uphill until you realize you are in the mountains.

We like US 27, that way you don't have to go through Atlanta. Plenty of ACOE cg's along the way.