Max Shutter speed
Panasonic GM5 can shoot continuously at max speed of
5.8 fps and has max shutter speed of
1/500 sec. GM5 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 GM5 doesn't have a built-in flash but it has a flash shoe for mounting external flashes.
Focusing
Panasonic GM5 features a Contrast Detection autofocusing system. The AF system has 23 points to choose from.
Panasonic GM5 also features
Face detection AF where it intelligently detects the faces in the frame and locks the focus automatically.