Pi 5 pins 2 and 4 can provide 5V unregulated from the USB C or can be carefully used to power the Pi since it bypasses the regulator. Devices that embed a Pi, like the sBitx transceiver, power the Pi through pins.
The Pi uses 3.3 V logic and can provide 3.3 V on pins 1 and 17 with a total max current of 500 mA. The GPIO pin logic is 3.3 V and a pin can source up to 16 mA on a pin and 50 mA total.
Pi hats are often powered through the Pi pins.
It looks like the USB C connector has soldered connections so it might be done but I haven't done it.
73
Bob KD8CGH