Well, the optimal throw for maximum distance is a high s-curve. Any pro will tell you that. Throw an understable disc high, it'll turn and glide a long way before starting to eventually fade. However, I'm not sure about the actual angle. I'd say the golf angle of 15 degrees is pretty close. Could possibly be a bit higher. Some of the videos of the distance comps show them launching the discs way high. Throwing level is definitely not the optimal angle tho. Having that been said, most of my throws in a round are level (golf shot) and not high (max d) to preserve accuracy.
And I agree, the physics of disc golf are alot of fun.