I do know that from speaking with our RC, they would do NJ only on Tuesdays, so it led me to believe they also did the Northeast on the same day. I don't know about other regions though. Then by Thursday night when the portal goes through it's maintenance time is when they upload the portals to any new appointments.
I do know that the earlier your file is complete (minus the nom) and you're placed on NWL, once you receive a nom, your file will be looked at in the order it was placed on the waiting list. Early bird gets the worm as far as easing any worries. Also, if your region is competitive and your Whole Candidate Score is close in numbers with another applicant, they will wait to see who's numbers rise from their 7th semester grades. DS received his appointment earlier without an LOA because he was significantly higher than other applicants who received noms, and he was very early in being placed on NWL.
When DS received his appointment, they went over his file on a Tuesday, got the call from the Congressman the next day on Wednesday, then the portal updated by Friday morning. Hope this helps!