One thing that is clear to me is that the Finsbury Park to Welwyn Garden City slow lines are turned have had relatively simple stopping patterns turned into a complex mixture of odd patterns in order to allow the Cambridge Slows to stay off the fast lines across the whole section. This drives the need of the trains to skip Oakleigh Park and New Southgate at times and run non-stop from Welwyn to Potters Bar at other times. This is to get the trains to Alexandra Palace southbound or Welwyn Garden City northbound just in front of the following Cambridge Slow. There will be much passenger confusion, at least to start with. Thus there are oddities, such as a Cambridge Slow calling at Hatfield, being followed by a Moorgate train non-stopping Hatfield! To be fair, some of the most unusual stopping patterns are in the 'counter-peak' direction. The counter-peak direction does see quite a few services that are currently empty stock (and thus non-stop throughout), running as passenger services, hence some of this complexity.
Overall, just this one section, involving only two of the four tracks highlights how the timetable will be tight in so many areas and thus prone to unreliability and why run times for several flows are lengthened, but in frequency terms not that much has been added at peak times. It is frequency increases that passengers really respond to and drive passenger growth. Run time lengthening without frequency improvement will tend to suppress growth and adversely impact revenue.