The radio can be the only thing plugged into the 12V/2A ports. The 5V/2A ports are available to use. That being said, I don’t recommend connecting anything other than the radio to your main VRM. You don’t want to lose a match because your rpi wiring shorted and crashed your main VRM, taking the radio along with it.
We use this buck-boost converter (or something very similar) to stabilize the voltage from a PDP branch circuit to any voltage between 1.25 - 20V. It claims to be able to provide up to 5A; I can’t confirm that but we haven’t burned one yet. This is how we’re powering our Jetson and LEDs this year.