Now that the 15 has USB-C, I’d like to see if it correctly supports USB-PD. Is there any way to tell the charging speed when you plug in your phone to charge? With my Android it would say “Charging Slowly”, “Charging” and “Charging Rapidly” or I could use some apps. I haven’t found anything with my iPhone though.
You can get usb-c to c charging cables that tell you the wattage on the cable, no way in iOS itself I know of.
Be aware that charging speed will vary on all devices in accordance with what the battery controller thinks is best at any given time.