Max Shutter speed
Nikon 1 S1 can shoot continuously at max speed of
15 fps and has max shutter speed of
1/4000 sec. 1 S1 also has an electronic shutter which can shoot silently at max speed of
1/16000s. One thing to keep in mind is that electronic shutter may cause rolling shutter / jello effects, and also banding issues under artificial light on your images.
Flash
Unfortunately 1 S1 doesn't have an external flash shoe so you are limited with the built-in flash.
Focusing
Nikon 1 S1 features both Contrast Detection and Phase Detection autofocus (AF) systems which ensures speed and accuracy of focusing in most situations. The AF system has 135 points to choose from.