If I am using the same Apple ID will erasing an old iPhone will it effect my new iPhone?
If I erase all the data in an old iPhone using the same apple account on my new iPhone will it effect my new device?
iPhone 7, iOS 14
You can perform all of the steps in the following on your old phone and it will not affect your new phone: What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support