Yes, because the Mate20 Pro and S20 both support USB-C interface charging, and the chargers of both comply with the USB-PD fast charge protocol, so they can be compatible with each other. However, it should be noted that although both chargers support fast charging, the specific charging speed will still be limited by the device itself, so there may be some differences. At the same time, in order to ensure charging safety, it is recommended to use the original charger or a third-party charger that meets the relevant standards.
Under normal circumstances, we do not mix, the power of each phone is not the same