Wireless charging harmful?

It´s really up to you, whatever is most convenient! When sitting at my iMac I connect my iPhone to it and charge it that way...it seems to charge faster than putting it on my wireless charging pad. And I have heard that buying a cheap no-name wireless charger can harm the iPhone (overheating etc.), which is why I bought a Mophie wireless charger pad at my local Apple Store here in Germany, for €44,95 (about $52). And kb1951 is absolutely right...you can't overcharge an iPhone, either cable charging or wireless charging. Hope this helps you! Regards, Ian.

You can charge it either way. There is no harm in either method. You can charge it at any time and for as long as you wish. I plug my phone in for charging every night when I go to bed and have a full charge in the morning. You cannot overcharge it. I am not sure what you mean by the ‘20-80’ rule.

There is no harm in wireless charging.

Whenever it is not in my pocket, my iPhone is on my wireless charging pad.

Previously in the same situation, it was connected to my charger via a cable.

I believe the 20-80 rule is that you don't let battery get below 20% or above 80% as some "experts" claim that this will prolong the battery life.