what is safest charger for iphone 7 plus

if it does not produce a voltage over 5volt it's safe

amps are pulled so if it can deliver 1amp it's enough people report iPhones charge a bit faster with the iPad charger which is 12watt so 2.4amps but I doubt any higher amps will help.

about quality then people post issues once in awhile with cables that are melted and chargers that are blackened this is not really possible to happen with 5volts so it must mean that some ac chargers are defect and poor quality would be leaking AC 110/230volt rather then 5volts which would explain the melting, also if they deliver spikes in the 5volt that could also damage a phone so too cheap is a thing.

Hi. Yes, there are so many to choose from. Stay away from "gas station" items. The safest thing to do is to make sure you select a power brick and/or cable that states "Apple Certified" or "Made for Apple". Spending a few extra dollars for a quality item is much less expensive than the cost of replacing your iPhone or your home that burned down because you used inferior charging equipment.

I've been using a myriad of chargers for years and I've found that they don't make a lick of difference. The cable is another story - use an Apple cable or one certified by Apple.