I never consistently saw the show so I only know from youtube the many deaths and rebirths of Prime.
Ultra Magnus really does not look great in the movie. He is just sort of there and to set up Rodimus.
I have a good time watching it anyway. I am not aware of other scenes, but not shocked that there are some.
Magnus is a good field commander, if he had time he could have developed into a good leader of the Autobots, though he doesn't have a "prime spark" like Op or Rodimus
As to Op, he perishes in the movie, he speaks from the Matrix in the movie, Rodimus does chat with him in the Matrix in Five Faces of Darkness part 4, is brought back as Undead Optimus in Dark Awakening, then really revived in Return of Optimus