I'm redesigning a form that is used by office workers who interview respondents in person. In some cases, there will be two respondents.
The current design is (2). My suggested approach is (1).
a. The interviewer usually asks each question to each respondent in sequence
b. This is (unavoidably) a long form, with many questions
c. Important: each question may lead to a subsequent question -- depending on the respondent's answer. Follow-on questions are hidden by default, but displayed progressively. Thus, respondent 1's first answer may lead two "new" follow-on questions, while no follow-on questions may be displayed to respondent 2.
d. I will conduct usability testing but for now I'm looking for guidance