Hooking up a Raspberry Pi 3

I have a RPI3 being used for vision processing. Right now, I have it hooked up via a 5V 3A DC-DC converter that is wired into the PDP. It goes from bare wire to micro-USB, making it an easy thing to hook up.

I know the VRM has a 5V 2A output as well. 2.5A is recommended for the Pi3, but I am guessing the VRM output would work fine. Would I just cut up a micro usb cable to hook it up there?

In either case, wouldn’t the Pi count as a custom circuit via R49, and need to be behind a relay? I am not exactly sure what the purpose of it would be, but want to make sure that whatever I am doing is consistent with the rules.

Yes you would just cut the micro USB cable but make sure you keep track of positive and negative when you cut(I have found some cables do not have a red and black cable but instead have the same colored cables)

Yes it would be a custom circuit(as the rule states, anything that is not part of the control system or an actuator is a custom circuit (e.g. cameras, leds, seperate computing devices, etc.)) but it does not read a relay that, you would only use one if you want to turn it on and off

No need to do this. Just solder some wire onto the 5v/ground pins.