I think its going to be different for everyone. One size does not fit all. As I posted in another thread, I was in a tournament, and we had a temp hole that was about 90ft. I threw a putter, and everyone else threw a midrange, and I was playing in Intermediate, so I know I was not playing with beginners.
As far as using drivers and Mids as putters, that is a bad idea. drivers are very hard to control if thrown as slow speeds, and both drivers and mid ranges will tend to blow way past the basket if you miss the basket.
The best thing you can do is go to a football field, or an open field and mark off distances and see how far you can throw each one of your discs. That is one reason that regular golfers go to the driving range, to see how far each club drives the ball. You need to do that with you disc so you have an idea of what each disc in your bag can do for you.
Me personally I reach for a driver on any hole 275 feet or more. Below that, I throw a Dx Viking and use it as a Fairway driver. I used to throw a TL , but I really didn't care for it.
under 225-160 I throw a midrange. Under 160-30ft I throw my Soft Magnet, my main approach disc. Under 30ft I throw my Pro D Magnet putter.
Like I said, everyone can throw different and fell comfortable throwing different discs on different shots.