What is the form of the Angel of Death, and are the moments before and after the soul is seized terrifying for both the believer and the disobedient, and is the questioning by the two angels frightening depending on one's deeds?

There is no textual evidence from revelation that describes the form or appearance of the Angel of Death. The state of the righteous and the disobedient at the presence of death differs according to their piety. For each are degrees according to what they have done, and He will fully repay them for their deeds. The state of a person at the appointed time of death corresponds to their actions.