In regard to the Breen, I would note that Star Trek Adventures: Klingon Core Rulebook says “They only present themselves to non-Breen in full-body suits that hide their identities, and their bodies disintegrate when they die while wearing those suits. While this is an admirable trait – it means Breen cannot be taken prisoner, an attitude in line with the teachings of Kahless – it has made it impossible to determine the true face of the Breen.” This is a pretty cool explanation for how Worf could be right even after Kira and Dukat stole their suits.

I know STA isn’t canon but I still like this reasoning.