It's probably the case that this was good intent given the lack of desktop ARM computing hardware, but they really should let the client decide the video quality.

I doubt ATO is going to have a significant impact on headways. There might be some minor impact if they include automatic door operation. The looming budget crisis due to low ridership is going to dictate headways/levels of service more than ATO.

I do look for forward to smoother train rides, especially not having operators lurch the train to a stop to avoid platform overruns.

As for Rosslyn I don't remember WMATA ever going below 2 minutes with ATO. I believe the switch is around ~130 seconds to set.