About the only thing I can find off about Vader's armor is that the cap and chain are under his helmet for Rogue One, but around his neck over the helmet part in A New Hope. Maybe it come loose during the fighting and was suppose to be under his helmet, but after coming back to his Star Destoyer following the capture of Princess Leia, one of his troopers said "Hey Darth, that cape looks really wizard." And Vader decided to keep the look.