Depends on where you're staying, but Mr. Cues II in the Chamblee-Tucker area (NE Atlanta) is a big one. There's also the Red Fox up there--although I have not been to it.
Another that I have not visited yet is the Pool Turtle in Decatur. It is very new. Decatur also has Twains.
Downtown, near Piedmont Park (10th and Munroe), there is the Independent. And westside there is the Whelan, although they only have three 9-footers.
NW outskirts--beyond the 285--in Marietta: Cues on Canton Rd, and there are a couple of Mazzy's--one on Roswell Road, and the other farther NW in Kennesaw, off Wade Green. And, farther westward on Wade Green there is Kennesaw Billiards.
Westward on the I-20, you can find Stix in Villa Rica. Only been there once, to meet up w/
@iusedtoberich. Liked it enough to go again, although it too far to want to.
If it's a consideration, Cues (Canton Rd, Marietta) is still a smoking place, not sure about Kennesaw Billiards, but I don't think any of the others allow it.
Tournament-wise, I know Cues has a big 9-ball one on Saturdays, and I think it starts at 5pm and will probably run until after midnight. Mr. Cues II should have some, but I don't know their current stuff. I also know of smaller bars/restaurants that run tourneys for house cash, like Varner's (in Smyrna; Mon 9-ball 7pm and 10pm--normally single-elimination, race to 2; Wed 7pm and 10pm, 8-ball, single-elim, race to 1), and Sidelines Sports Grille (Barrett Pkwy, Kennesaw; Friday 8-ball, 9 pm--used to be 8 pm, so check w/ them...I think it was race to 2, when I went).
The house cash places are of course on 7 foot tables. Mazzy's has 8 footers...at least, I know the one on Roswell Rd has those. The other are mixed, but mostly 9-ft w/ some 8's as well.