I can't speak for ATL specifically, but in general the 75/76 (7ER) fleet seems to fluctuate the most in terms of monthly block hours vs other fleets. You will fly your a$$ off during the summer and then wonder if you still have a job in the winter.

As far as trip types, ATL is like most other 75/76 bases. Lots of 2, 3, 4 and 5 day domestic trips with between 1 and 4 (rare) legs per day. Lots of Florida and West Coast/Trans-cons. Some Caribbean/South/Central America flying mixed in there too. Quite a few red eyes but avoidable if you don't like 'em. International trips typically run 3-6 days over to Europe and some deep South America. A three-day might be something like ATL-MUC-ATL whereas a six-day might look more like ATL-AMS-BOS-CDG-ATL. As you might suspect, the international stuff tends to go more senior but it can be had in some form at almost all seniority levels, if that's your jam.