Max Shutter speed
Leica SL2-S can shoot continuously at max speed of
9 fps and has max shutter speed of
1/8000 sec. SL2-S 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 SL2-S doesn't have a built-in flash but it has a flash shoe for mounting external flashes.
Focusing
Leica SL2-S features a Contrast Detection autofocusing system. The AF system has 225 points to choose from.
Leica SL2-S also features
Face detection AF where it intelligently detects the faces in the frame and locks the focus automatically.