I would be careful with sexing by fins alone as they may be local variations or have been injured and not grow back. I know of cases where people thought they had bought a male and a female mandarin only to find out that the suspected female was a male with a damaged fin.
And I would also be careful with taking the thickness of the black bars as a sexing indicator. While it is true that males have stronger and wider black bands the regional differences can be even bigger. So this only works when you know for sure that the fish in front you come from the same location.
On angelfish and especially dwarf angels there is a much better way: body proportions. Males are more stretched out than females. At the same height they are usually 10% to 25% longer.
This can be seen best on
Centropyge argi and its close relatives.
To get an idea of the sex differences check out images of
Centropyge loriculus and compare them.
Also to consider is that (almost) all angelfish females are in general capable of changing into a male if they are the dominant individual of the group/pair.
When pairing fish always introduce the larger sex (for angels and butterflies that is the male) to the tank where the smaller (female) has at least been for a day.
So if you have one that is slightly larger than the other and both don't look stretched out like males I would give it a try and place the larger one into the tank with the smaller one. To play it safe you can use a glass plate to partition off a corner/side where you introduce the larger one and then observe their behavior to each other. If the smaller one makes submissive gestures (body turned slightly on the side and into an "S" shape) and the larger one doesn't make any attempts to attack they will most likely get along.
Just in case I would recommend to always do this in a tank that you can quickly take a part to separate them if things don't work out.