Couple Topics (Letoff and App)

First, my bow has two let-off settings. One is 65%, and the other is 80%. As of now, mine is on the 65%. My question is - if I get this changed, will it negatively affect my arrow velocity?

Second, does anyone know if there is a range finder App for android?

You might loose a smidge of speed. Nothing to worry about. But check your sights.

search ranger finder and a deer and golf one pops up its pretty neat idk how accurate it is though