Regarding ATL - My advice is to go through the main checkpoint on the domestic side. Despite the fact that they added additional MMWs this past fall, it is still a fairly easy SDOO because they don't have enough staff to operate all of them. I passed through the main checkpoint 5 times in the past month, and there were multiple MMWs roped off each time I went through. Also, during peak times, see if lane 20 (left side) is open. It is WTMD-only. Note that all gates can be accessed from this checkpoint.
Don't know how long this will last, but it's definitely the way to go in ATL these days.