What would be the success criteria for user testing for 2FA authentication

i'm conducting a user testing session for a few prototypes. one of the prototypes of a feature i'll be testing is the 2 factor authentication.

Compared to other features which have more of an information or value element, 2FA seems to be a more of a security and intermediate feature.

i'd like to know what factors should i be testing for and the questions i should be asking for this feature. Some factors i'm considering are

  1. Does the user perceive their app environment is secure after 2FA authentication
  2. Ease of use for users to get authenticated with 2FA (on a scale of 1-10)
  3. Clarity of error messages when users encountered them