unless you are a really big fan on Asian food* there really isn't much of a reason to hang out in Duluth for the entire weekend. If you tend to drink or do "other" at concerts you may want to grab a room by the Infinite energy center for that particular night. There is no public transport worth taking from there to the City proper. If the concert is Friday you'll want to head up early, traffic is a nightmare out that way. I'd stay in or around Mid Town all but the night of the show. I am going to the same venue for Gorillaz later this year and intend to get a room out there as well. You could conceivably stay in Mid Town and Uber/lyft/cab back and forth to the show but it will be expensive and again if on a weekday a hell of a commute. Mid Town is really the best place for tourists here IMO. Downtown rolls up the streets at night as there aren't a lot of residents. Mid Town has the best restaurants and the easiest access to Atlanta night life and is a safe walk able area. Ping us closer to the event and we can help with particulars.
* the asian food out in Duluth is pretty incredible and I say this as a guy that lived in Asia for a while. Great Korean BBQ (Honey Pig), Great Korean Fried Chicken AKA KFC (Thank You Chicken - really that is the name) and Ramen (Umaido) for a start. Lots of other great places as well
So I just looked and the concert is Sunday night (boring con call) go stay in Midtown Friday, hang out in Atlanta Saturday, head up to Duluth Sunday afternoon and grab some really good Ramen on the way in I recommend the Tori Ramen with added Fried Chicken. Going to guess that you may have a taste for music/record stores. Criminal Records and Wax n' Facts are both good shops in little 5 points. Wax n' Facts has been around so long that it is where I bought records in High School. The entire Little 5 area can be fun though a touch sketchy in the hippy drug scene kind of way. Junkmans daughter is an Atlanta institution worth checking out, the Porter is a great place to eat with a great beer selection, wrecking bar is close by and a hell of a brew pub and of course there is the Vortex which has the benefit of being 21 and up and offering one of the few remaining smoking sections if thats your thing. Lots of great music venues and whatnot. For Latenight hit the Cafe Intermezzo in Midtown for Desserts and nightcap drinks, iirc they are open until 2 or 3 on weekends. I really like the W Midtown as a hotel. Wife and I get rooms there now and again for nights out when we are doing something in town. I like the location and the Bliss Spa in the building offers a good massage which is never a bad way to start a weekend.