I'm hoping a cable is a cable when it comes to USB-C to USB-C and FAST charging (I assume it'd charge slowly no matter what). That was NOT the case with USB-C to Lightning cables. In order to get fast charging you pretty much had to use Apple's version as back when I looked there were no mFi certified USB-C to lightning cables, and a couple of games I was playing would outdraw and discharge faster than they could charge if I were playing even while plugged in. With Apple's cable and power adapter, I could actually charge the iPad while playing.
I'm hoping that whatever was required for fast charging in lightning was something special Apple was doing with its connector, but not USB-C is hopefully just USB-C.
Edit: I actually didn't see very many USB-c to USB-C cables that were over 2 meters out there anyway, but didn't look too hard. Thought it was odd Apple was pushing Belkin's cable on the suggested accessories page when they do offer a 2 meter USB-C to USB-C cable.