Another quick one here. Just wondering if both of the above are appropriate ways to voice the question 'Where is the man' (as well as contextually similar questions). Thank you!!
Though your point gets across with both structures, one comes off more unnatural than the other.
By inserting the 男の方｛かた｝ (see below for why I don't use 人) into the middle of どこにいますか, you break up the flow of the sentence, and risk loosing what you are originally trying to ask. It's better to put 男の方 in front of どこにいますか.
Additionally, 男の人 is also unnatural sounding to me. Usually, when you're talking about a man, you say 男の方｛かた｝. 方 is more polite and respectful. Additionally, 人 doesn't specify one person. You could be asking if there are multiple men there. I would say the difference is the difference between saying 'man person/people' (男の人) and 'man/gentleman' (男の方).
The usage of が in this sentence seems to be okay though.
This is much more natural sounding, especially if you replace 人 with 方.
Could either どこに男の人がいますか and 男の人はどこですか be used?
Yes, the emphasis changes though. In the first sentence, let's say person A is talking about a man, as if he is visible, and person B can't see the man and says "どこに男の人がいますか" as if puzzled by the situation and the man that she can't see. It's strongly emphasising the "where" part. The second sentence is more neutral, as if just asking where some man or another might be.