Adding and USB-C QI-adapter is a possibility, but not for me, I want to be able to use the USB-C port for other topics, as example screen, or to deploy, debug apps. I don't want to have that hassle, to plugin in and out.
The Qi efficiency is between 60% and 95%, depending on the charger, I also don't see any heat issues with my chargers, they are not cold but by far not "hot", only in the car when the navigation is on and its charged... then the phone heats up, independent if I use a cable or not.