To answer the above sentence, would the sentences below be acceptable?
Is 1 the only acceptable answer since the question is in past tense?
Both are possible, and the choice will depend on the context and the mood. (Why is the first question in the past tense?) If you are objectively saying "Yes (that is right)", そうです is the natural choice. But そうでした is also fine in the following situations:
I would say
because it means
Yes, that is correct.
はい、そうでした may be ok but it sounds a bit strange to me as it sounds like
Yes, that was correct.
Other answers I may hear people say would be