hi there and I will share my experience. I had a plec which grew and grew. Then I got some discus which were just awesome. One day I walked into the room and the plec was hanging off one of my discus.............sucking the slime. So the plec was given away to a good home..... I would definitely NOT put a plec or chinese loach in with discus or angels.
Beautiful though the plecs are, they are not good companions for discus.