No. The phone itself supports chargers over 18w. So it's okay to use this 20w charger. In addition to the fast charger, it can also reduce the charging time. However, generally fast charge has a greater impact on the efficiency of the battery. The rest is fine. It can be used with confidence. Apple officially also supports the use of fast charging appliances for this phone.
Hurt. The 20w is designed for the iPhone 12 series. Previously, Apple's mobile phone was officially equipped with a 5-watt charging head of 5 volt 1 amp.