Can't help you with your gun, sorry.. but I can help a little with the explanation I think.
Extended chokes have a longer taper, usually around 3" or more vs 1.5'-2" for flush. This lets the shot/wad come down to a smaller group leaving the barrel and equates to a denser pattern. I'm not sure of that makes sense or not, tried to word it as simply as possible. Sometimes they are no advantage over flush chokes, sometimes they are 20 times better. Just have to pattern and find out what works best for you. GENERALLY they give you a more even pattern vs the same constriction in flush.
Now add in patternmaster and wadwizard and you have a whole new ballgame. Those are stripper chokes. No, not that kind of stripper
. They have small studs in the extended part of the choke that grabs the wad for a split second, letting the shot separate from the wad quicker which usually makes denser patterns. That is how it is supposed to work, again you have to pattern to see if it holds true with your gun and ammo. The first thing I noticed with my patternmaster was the lack of a super long shot string. I don't believe it has any effect on waterfowling, but just something I thought I'd throw out there. I shot a cripple with it and it was a small explosion of water on the bird vs a long string of a splash in front and behind the bird. I really would'nt suggest it for a cripple finisher, I blew the head/back to pieces at 20 yards. Bloody mess.