no manual, sorry, thought it didn’t really need one! i’ll put something together.
power: whatever power you supply will be used to power grid/arc/keyboard or whatever else you use it with. so the power requirements are determined by what you connect to it (grid 128 can draw up to 600mA, for instance).
you can power it either from a regular USB power supply via the USB B port on the side, or you can power it from eurorack power - but not both at the same time.
if you power it from eurorack it will require +5V rail (and again, make sure you have at least 600mA available on +5V rail).
not sure if this answers your question? or are you asking if 2 > 1 would convert 12V to 5V? no, you have to have a powered +5V rail.