Bounce when possible and typically angled so that the the flash is aimed at a spot halfway to the target. Ceilings are most often used, but walls can be used too.
For candids, flash is lifesaver when the subjects are strongly backlit. Without the flash, the subjects are either underexposed or the background is blown out. Learning how to use FEC and EC together to balance the subject brightness and background brightness will improve photos a lot, even if the flash is located on the camera and pointed directly at the subject.
Flashes have a zoom coverage range, and it is a consideration. The 430 covers up to 105mm while the 600 covers up to 200mm.