I finished S2 this weekend - one of my favorite shows on TV. Their attention to detail is amazing - the guys playing each of the historically famous subjects were dead ringers.
The interview with the BTK survivor was one of the most intense TV moments I've seen in a long time.
Last year I listened to a podcast on the Atlanta child murders called Atlanta Monster - the podcast eventually fizzled out by teasing all sorts of bombshells that never appeared and/or floating totally unsupported theories, but it also had a huge amount of detail on the crimes and law enforcement efforts to catch the killer. All of that was portrayed to the letter in Mindhunter S2.
There is a quick scene in Ep 6 where Wayne Williams shows up with a camera to the crime scene 2 episodes before he appears as the main suspect.