In addition to what goober said which I completely agree with, an NTRP rating is ultimately based on results against other NTRP-rated players. No NTRP points are assigned for style that I know of so watching video can be misleading. Only results matter.
Are there no 3.5 NTRP players in your non NTRP leagues and classes that you could look at and/or hit with?
When should you serve and volley in doubles? Only when you want to win.