As an Atlanta resident I agree with most of what has been said but also have slight differing opinions. First, I take 285 in either the far right or second from left lane. I’d rather be in the second from right lane but it’s badly torn up between 75 on the south side and 75 on the north side (on the west side of the city). I hate 285 but still prefer it to going through the city towing the trailer, and have done both routes. Be prepared for ppl to merge at 30mph and to brake at the I20 intersection because nobody can drive anymore.
Please, please, please do not be in the far left HOV lane. You are impeding traffic, and even though they rarely ticket you are not supposed to be there with a trailer. The express lanes are similar but will ticket (photo) every time if you drive in them with a trailer.
My preference in your case would be to do one of the alternate routes proposed. Or even consider coming up 75N, then taking 285W to I20W and on from there. The Bama route is better than the Ga route if you plan a little more time.
I’m in the before 6 (through the city before 6) or after 8pm camp. 285 is usually fine by 8pm even with Braves games. Mid-day can also be ok traffic wise but the drivers, despite there being less of them, are demonstrably worse - so early or late for me.