What wattage adapter is compatible with my iPhone 16e?

all of them really

haven't tested the as low as 5watt charge my current iphone17pro really but it sure worked fine with my iphone11

and about how high then there is no upper limit really

Watt  is like how fast your car can drive, but the speed limit is how fast your car do drive

the iphone draw as much current as it was build to use when charging, the fact that a

charger can provide a lot more just means it's not having its full capacitive

used

some of the newer devices have some extra fast charging at 40watt chargers

normal fast charging is when it's over 18watt

you can read more here Fast charge your iPhone - Apple Support