You can take the bypass but it is busy traffic too and adds miles to your trip. We just go straight through. If you have 2 or more people in your car you can use the HOV lane which is on the far left. This will take you straight through on 75. At one point it goes off on its own and then rejoins You don't have a lot of merging traffic in this because of the limited access. We have far fewer issues driving through Atlanta than we have with Chattanooga where the amount of lanes isn't enough to handle the traffic and there are back ups.
My advice is to drive straight through on I75, use the HOV lane (if you have 2 or more people), and go through whenever you get there. If I could avoid rush hour that's nice but if you reach Atlanta during rush hour it's still doable.