Hmm. The chorus part could be an extremely fast vibrato, but imo it sounds unintentional and more like he is struggling to hold the notes. Could be that if he has a lot of adrenaline in his body, it will affect the vocal chords, just like being nervous. To be honest, that is what it sounds like to me, not really a specific technique.
If it is indeed a technique and on purpose, it's bascially just a very fast vibrato.
As for the guitarist, it's difficult to hear what part he is actually singing since there are more than one back-up vocalist, but the one you are referring to sounds like a Fry Scream / Distortion Overlay.