choose navigation type on navigation screen and on route picker
To switch between Shortest or Fastest you have to go into settings->navigation->type and choose shortest or fastest. I often switch between these modes when picking my route so it would make sense to have that option available in the same screen as where the routes are chosen AND on the "navigate to" screen.
Oleg Prostakov commented
It's also a good idea to put option "Avoid major highways" to the Navigation screen. I use both car and motorbike and every time have to switch this option through the settings menu.