A fast arrow is no more or less accurate as a slow arrow. The accuracy part comes from the technology needed to obtain the speed, ie. short brace heights, higher poundages, lighter arrows. All of these make the bow harder to shoot, harder to maintain.

Accuracy comes in the form of the shooter with repetition. I am no more or less accurate with my 330 fps set up as I am with my older 275 fps set ups.

As for broadhead flight, accuracy comes in the setup, tuning and fletch. The quicker you get your arrow spinning out of your bow, the sooner and quicker it stabilizes in flight regardless of it's flight speed.

Point A (bow) to point B (target) is what it is regardless of how fast the arrow is flying. It's what it takes to get it there is where accuracy is deteriorated.