If you put your flash on top of your camera (or attach the flash with the camera using an ETTL cable) the camera will recognize the flash fix the shutter speed at 1/200 sec. You can go for a slower shutter speed if you use M or Tv, without any problem. But if you try to go for a faster shutter speed than 1/200th sec (1/250sec in other cameras than 6D) in M or Tv mode you will get a black unexposed part on the frame. To just use your flash as a fill flash you need to reduce the flash power in the flash (or with flash menu in camera). If you want to go for a faster shutter speed than the limiting flash sync speed (1/200) then you need to go for High Speed Sync (HSS) capable flash. There may be other ways of doing it, I do not know. Someone else will probably point you to those directions soon.
Correct. Here a a good video on HSS. It is a PW ad and you do not need PW to make it work when the flash is on the camera. After about 6 minutes it gets into stuff you don't really need to yet unless you are interested.