What often happens currently is number 1, but usually minus the first sentence:

- The specific ones gets closed as a dupe of the general one, but no clarification of the specific point happens.

So my preferred approach would be your number 1:

- Answer or edit an answer to the more general question such that it addresses the more specific question. Then close the specific question as a duplicate. 

I think this makes the most relevant information available in one place on that topic.

Where both questions already have answers, closing as dupe and then merging works well, as you end up with one question, and all the answers from both,