What are the usb C cables for on the Kamiq? charging a phone or connecting to the infotainment system?

I have heard you need very good quality cables, but which ones?

Both, usb c is the new standard but you can get adapters that convert it from the old style usb A. 
 

good quality cables yes in terms of their construction if you want them to last but same with hdmi no need to pay over the odds sucked in by promises of better sound etc, and certainly no need to be paying dealer prices.