Can the supply voltage be unregulated and float between 5VDC and 12VDC?
Yes, you can. 5V is not recommended. Some dummy 9V or 12V adapter will work.
Doesn’t the Rock Pi auto-switch between 5,9,&12 VDC and have its own internal voltage regulation?
For QC, currently we select 9V because it’s the most common. For PD, we request 20V first, if not then 15V, then 12V, then 9V.
Also saw something about QC needing two way USB-C communication?
QC use D+/D- for communication. So the usb-c cable must have data wires.