Finally, on the topic of rail first shots. Rail first shots add a variable and are in general more difficult to control. Now, there are many cases in which they also eliminate other challenges (speed of the hit, establishing the right angle with a rolling ball instead of draw, etc). If the rail first hit eliminates more challenges than it creates it is the right shot. There are clearly many, many times this is the case. And sometimes you need to play shape for an angle that sets up for a rail first hit. Maybe other balls force you to play shape along the rail, or it is the most natural position to obtain from the prior shot. In those cases, yes, know your rail first shots. They are common and should be totally comfortable.
But I wouldn't go so far as to say I prefer them. I can't remember ever shooting a rail first shot with ball in hand. My cue ball is pretty good so I usually get the angle I want, and I don't play rail first as often these days as I used to because I know the other hanging shots so well.
Dr. Dave pointed out that if you want to come out at an angle, play shape to be on a rail, if you want to come out along the rail, play shape for an angle. Do this when possible and you'll be able to get where you're going. If not go rail first and get the job done that way.