The rerouting trigger is currently 200 meters (plus positioning accuracy), polled every three seconds. 200 meters is about a block and a half in a common city center, or way less than motorway exit spacing. So, how many blocks late do you see rerouting happening? What's your positioning accuracy (see bottom of the screen, below the speed)? You're not expecting to catch the very next turn, are you? Do you have experience with Google/Apple/HERE maps, what's the trigger there? I don't want to add an option, there should be no need for such, but we'll of course change the default if it's bad.

No, not with raster maps, and it's too early to talk about vector maps.