Gale, I just saw your post & didn't know when you were leaving but I live in Snellville which is beside Stone Mountain in the Atlanta area. My husband & I both worked downtown years ago & there is no really great way around Atlanta.
As others said, it really is best to stay off I-285 because of the trucks & it's like a raceway-except when there is an accident & those are very frequent.
One of my son's works downtown & he put an app on my IPhone called Waze that tells all kinds of stuff to help you in driving. We used it last week traveling to FL & back & were glad to have it. It tells where accidents are, traffic & other things to avoid & ways around.
Have a good trip.
Joyce T

Lol....just drove through Atlanta for the first time in January....ignorance is bliss! It was my "turn" to drive and hubby was asleep....it was pouring....I white-knuckled it and stayed in a middle lane and prayed-a lot!!! Good luck! Safe travels!

Went through Atlanta several years ago on a Sunday morning around 11AM---80 MPH---bumper to bumper---NOT going there ever again

Driving to FL many many times. I now boycott Nashville and Atlanta it's just a mess and nuts. Luckily where we live we are able to avoid the fearsome 3 (Chattanooga) although only trouble with C was the terrible air quality DH & I both got sick from that.
We go through St Louis, Memphis, Birmingham head south for I-10 then east for I-95 much calmer.

While you're in Chattanooga, get out on one of their free electric buses and see the town. Or, go down to the river and walk around. Great, tourist-friendly town! Have fun!

I always go straight through town-- no large trucks and plenty of lanes. Stay right on 75 and "hammer down"!