Regarding Duplicate Questions:
When you find a duplicate question, you should flag one of the question as a Duplicate of the other. If you have the privilege to Vote-To-Close, you should exercise your privilege as such.
Which one should be flagged/VTC'd?
The one which is poorly asked, is poorly formatted, has poor grammar, is lacking in information and so on. Also take into account if one of the questions has a good answer for it. In short, flag as such which requires least amount of effort for both you, the community members and the moderators.
If you are flagging the question which contains some more additional information than the target question, if would be preferable if you also edit the master question to incorporate such additional information. In case you do not have the edit privilege and you are only suggesting an edit, then make sure that you provide an appropriate edit reason with a link from where you are incorporating those additional information. In the absence of proper edit reasoning which would help the reviewers it is highly likely that the Suggested edit might get rejected.
However, in this case, as of now neither of the duplicate questions have an Upvoted or an Accepted Answer. So, we can neither flag them as "it doesn't belong here, or it is a duplicate" nor Vote-To-Close them. In such cases, you may flag the question for Moderator Attention using the "Other" option and explain it. Moderators can still close the questions as Duplicates even if the target question doesn't have an Upvoted/Accepted Answer.
Regarding Duplicate Accounts:
We can have Duplicate or Multiple Accounts provided we are not misusing them. If you find that duplicate accounts are indulging in Voting Frauds or another kind of malpractice, bring that to the attention of Community by posting that on Meta and/or Flag one of the posts by them for Moderators using the "Other" option to explain the scenario.
Generally speaking, posting that on Meta should be preferred as the community at large can evaluate the situation and ensures that we can get the view-point of a large number of people.