i have and am currently keeping angels with Discus. Some will tell you it isn't a good thing to do.
I kept a standard Philipine Blue, Blue Ghost angels with my wild cross Discus that I sold back in 2013, and I am keeping five Altums with seven F2 Batata Discus now.
As to the Angels being quick the Altums are big and slow, and everybody eats just fine. But, I also have sponge pre-filters in my tank that the discus and angels will go to for a snack.
I don't feed the tank again until the pre-filters are clean from flake or freeze dried blackworm.
I also have a large stump, floating plants, plants growing on the stump for places to make the fish feel secure.... the Angels and Discus also actively hunt any pond snails that are in the aquarium.
Again some more experienced than I will tell you it is a bad idea to keep Angels with Discus.