I don't think there is any "best" way, but there's probably a way that will incite the least amount of confusion on behalf of your colleagues

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As far as I know, the first two options would give you the same result, but the second will be easier to explain ("the average score for HR was...", etc.).
You could also do things like find out who got the most perfect scores per capita, the fewest abysmal scores per capita, the highest median, etc. None of them could be described as "best", because each might suit a different purpose.
If I were you, I would go with calculating means.