All Apple USB C chargers are safe to use with all Apple devices. You can use the 87watt MacBook Pro 15” charger for your iPhone. Use the 30watt apple charger on your iPad. You can even use the 18w usbc charger for the ipad on your 15” Mac book pro (with limited results, but safe none the less). USB-C products approved by Apple are safe to use. They sense what they are plugged into and deliver the most appropriate voltage they can.