Hmm. You need to 1 pleco/tank. The clown loaches must in the 100G tank given their adult size is massive. Also the clowns might want a piece of your discus's slime coat so IMO they shouldn't be together. I've kept black ghost knife, they're pretty awesome, I guess they can be in the same tank as the loaches as they get pretty big themselves. I haven't kept the eel yet so no comment on that. As for the platy and the tetras i think they should go into the 100G as well, leaving the 75 just for discus.
So overall, IMO : 100G - 1 pleco, platy, loaches, BGK, tetras
75G- Discus + pleco
Discus need their water as clean as possible, so try to prevent putting too many fish in there (if you can) to reduce the wastes. I keep my discus with a few tetras, but it all depends on your waterchange. If you can keep up with it then it its alright. And for the loaches and the BGK, remember to quarantine before you add new fish, they are extremely fragile and get disease easily. I've kept my life long friend the 2yo BKG until i added an angel with fungus. I've manage to save the angel but the BKG died
