Please explain what voltage will the Rock5B SBC negotiate on the USB-C Power Delivery protocol for its power supply?
USB-C PD chargers normally output 3 amps total at any voltage. For 20V, the cap may be 5 amps = 100W. At 5V, the cap is 3A meaning 15 watts. (Ref https://www.hypershop.com/products/hyperjuice-100w-usb-c-gan-charger etc.)
How many watts does the Rock5B SBC consume altogether?
A M.2 SSD can peak at 7 watts. A USB peripheral can consume is it 15 watts.
If the USBC PD is 5V and the SBC is <~10W, I guess 5V USBC PD can drive the SBC with one M.2 and no power hungry USB peripherals.
Remember the 12V voltage for USBC PD is out of spec and most chargers will not support it. Instead, 15V and 18-20V are the standardized higher voltages in the USBC PD protocol.
Could it be useful that the Rock5 automatically negotiates as high voltage as possible (20V / 15V) and then contains a voltage stepper to bring it down to the SBC’s needed level (5V) - this would allow it to consume as much as 100W total which would without problem feed both USB devices and 2-4x M.2 devices too. Or is this in the design spec already?