I am concerned about plugging it into the arduino as it has this 'bridge' for voltage supply, the schematic is vague about that
Not sure if it is on one way to supply default power, or externally, I'll have to follow the tracks that may help..
The schematic is pretty straightforward [except for the part where they don't label the
Arduino headers very well - just like 98% of all other Arduino shield schematics I've seen
BTW], and it looks like you supply external voltage at conn J13 to power all of the
MOSFET loads. Normally, only the control signals come from the Arduino. Looks ok to me.
Alternatively, you can jumper JP2 and get Vin2 power from the Arduino Vin pin, if you want
to go commando mode.