M2 voltage conflict management?

Does anyone know how the M2 UTD handles both VIN (12V, from OBD-II) and USB (5V) being connected to power simultaneously? Is there any risk to the M2 or the laptop connected via USB?

If it can switch between the voltages automatically, how does that switching work? Is it “last connected” or “largest voltage”?

The main thing I’d like to be assured of is that I can arbitrarily plug and unplug USB for serial monitoring while the M2 is powered by the car. I tried looking at the schematics on GitHub but it wasn’t immediately apparent how this would work.