it's a good site for basic info but take it with a grain of salt.
discus and rams actually do well together. Particularly the blue rams..as their water requirements are very similar.
just keep in mind the tank temps and don't fudge on the low side for discus..they do prefer warmer water ..
I've raised discus for a couple years..I keep mine in a planted tank..yes not optimal as they tend to not get as large..I also keep discus with angels..yes angel will be fine in 84 degree water and can handle much warmer temps. if you go that route..keep inmind that angels may carry parasites that can affect discus(but I pretreat all my angels and discus with anti parasite meds as a precaution in the qt.)
some discus can be a bit timid..mine are definately not and all of them will beat the angel out when it's feeding time.