>>3263967depends on how much ambient light you want,
remember that the flash duration is anywhere from 1/1000s to 1/5000s depending on the flash. So when you're indoors and set f5.6 and 1/125s youre really just underexposing the scene and letting the flash fire a massive amount of light out for a thousandth of a second and letting all that light flood your film.
Im explaining all this to make it concrete that whatever shutter speed you use will not affect the exposure from the flash but rather the ambient light that is exposed. However the aperture will in fact affect how much exposure is drawn from the flash - I think you knew that though.
1/30s if youre standing still or on a tripod and want ambient light, depending on the scene you may need to compensate the flash exposure. In manual terms this means setting the metz to f5.6 but setting the lens to f8
1/60s for a balance of ambient light and flash
1/125s and above for the flash to wash out the ambient light
