Is the statement: "By Allah, if I were in your place, I would not have done this" considered a 'yamin laghw' (unintentional oath) or a 'yamin mun'aqidah' (binding oath), and is expiation (kaffarah) required if the speaker finds himself in the same situation and does what he negated?

What you said appears to be a type of oath sworn by someone who believes in their own truthfulness. This kind falls under "laghw al-yameen" (unintended or vain oaths), for which there is no expiation. A Muslim should guard his tongue from excessive oath-taking. Allah says: "And do not make [your oath by] Allah an obstruction against your doing good." (2:224). It is also mentioned that frequent oath-taking is disliked, as Allah says: "And do not obey every perjuror, worthless [person]." (68:10).