Hi Anonymous,
The biggest and most common mistake I see candidates making when trying to answer such kind of question is that they talk a lot of BS and I only hear bla bla bla as an interviewer.
One aspect might indeed be the pure "delivery" - i.e. how exaclty you communicate your answer (including voice level and intonation, body language, ...).
However, based on more than 10 years experience this is mostly only the symptom and not the underlying root cause. The real issue behind is that candidates are not able to draw a clear connection between them and the firm, and thus only talk about generic things that any candidate can say (like it's a great brand and intellectually challenging environment with top-notch C-level clients).
The trick here is to establish a clear connection to yourself, how exactly you fit in into this picture (e.g. what's your proof to be able and enjoy working in such an intellectually challenging environment, etc.)?
So far to your first question.
Q2: Sure, why not?
Hope that helps - if so, please be so kind to give it a thumbs-up with the green upvote button below!
Robert