Did your PSU not come with cables? General wisdom is to use the cables that came with your PSU. If you're trying to get a certain look, only order from be quiet! for your model.
The cables are molex terminated, and they go from 12pin to 6+2 (often with a second daisy chain for extra power). The reason you can't swap cables is some of those 12 pins will double up in the 6+2, and different manufacturers may have their pinout different from others. If your goal is to have prettier cables, getting a 12 pin or 8 pin extender with the pretty wires should be safe.
The SATA power connectors should be fairly universal, since SATA is mature and effectively EoL in consumer electronics, but I wouldn't deviate from the recommended wisdom.