Hi bro, Yes you can use 12W or 20W to charge iPhone 13 or any other model. Using original charger itself good and safe. also with original or mfi certified lightning cable. that can prevent any damage to the device or its battery.
Battery health may reduce suddenly after a few months, it depends on your charging practice as suggested in our battery health tips video.
Other than that, it shouldnt be a problem. You may use 12W or 20W charger.