Ok the not so short and not so rude answer...
Yes the birchir will get way to big for a 29gallon as stated by the coffee man, and some would say the discus as well. The angel or discus would be fine in your tank (IMO) but I would be hesitent for both, as discus do better in groups and angels in pairs (IME), and I'd always worry about the birchir getting nippy with a 40-60 dollar fish if you upgraded tank size and got the discus. If you kept the current tank best I could reccomend is ditch the birchir get 2 or 3 more angel and wait for them to pair off then sell/return the un paired. Hope that helps some
Andrew