I purchased an HTC 10 a few months back, and so now also needed to Quick Charge with a USB-C cable.
Meh, I don't really understand why Qualcomm pushed QC 3.0 on USB-C (I do get why Qualcomm wants this but why are manufacturers jumping in?!?). This quick charge technology is proprietary and requires the phone and charger manufacturers to pay extra licensing fees. USB-C already contains power deliveries specs and with the base cables, you get
[email protected] (15watts).
QC 3.0 has a maximum power of 18W. It uses variable voltage (from 3.2 to 20 volts) and the devices requests whatever it wants. It does make for a slightly more efficient charging but it's not really significant. For the record, QC 2.0 had fixed voltages : 5, 9 or 12 volts (always 18W max).
USB Power delivery (USB PD) has a lot more options (and more power). It supports 5, 9, 15 and 20 Volts. It supports up to 3 amps on 5,9 and 15 Volts and up to 5amps on 20Volts (that's 100W)
For the record, this is the car adapter I use :
Amazon.com: Vinsic® USB Type C Car Charger Adapter with Type C and Standard USB A Outputs For Apple MacBook 12", Nokia N1, Nexus 5X 6P, Lumia 950/950XL, and More.: Cell Phones & Accessories : Plain "old" USB-C so it has 15W of power at 3 amps on USB-C. You just add a USB-C to USB-C (important! don't use a USB-A to USB-C) cable and you're good to go.