Use 5V_P as the inner plane AC-GND reference for the USB2 and USB smartcard diff pairs, move the C1821 electroyltic cap from the back side near the edge to the front under the SoM where there is space available, make the 3V3_P copper pour occupy areas which allow the C1822 electrolytic cap to have a lower impedance connection to the regulator and M.2/mPCIe loads (as well as bringing 3V3_P closer to other loads), create a large In3.Cu keepout area on the top of the board where the antennae are