I’m assuming by inference that the two USB connectors are both ‘inputs’. Is there any auxiliary power output? (I have a ykush controllable USB hub that I use to power an external wifi and a hologram nova LTE-m module. I prefer that hub to get power straight off the power source rather than putting such a heavy load on the PI USB port as the latter causes under-power states on the pi)
You can use J7 power output.
J7 - 5V rated 2.6A max output, solderable pads on the bottom side.
Does the J7 output work even if the main power supply goes off (does it work with only battery power)?