Max Shutter speed
Fujifilm X-Pro3 can shoot continuously at max speed of
20.0 fps and has max shutter speed of
1/8000 sec. X-Pro3 also has an electronic shutter which can shoot silently at max speed of
1/32000s. 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 X-Pro3 doesn't have a built-in flash but it has a flash shoe for mounting external flashes.
Focusing
Fujifilm X-Pro3 features both Contrast Detection and Phase Detection autofocus (AF) systems which ensures speed and accuracy of focusing in most situations. The AF system has 425 points to choose from. Fujifilm X-Pro3 also features
Face detection AF where it intelligently detects the faces in the frame and locks the focus automatically.