Which is the proper translation for 委员会？
You are not the first person to wonder about the difference between 'commission and committee.'

https://www.quora.com/What-is-the-difference-between-commission-committee-and-council

Seems to me, in English, the difference is how they are formed: a committee is formed of volunteers, a commission is appointed. In China this distinction seems not so apparent, so they use 委员会 for both.

The original meaning of committ-ee was 'person to whom something is committed/entrusted'.
The original meaning of commission was 'authority entrusted to someone'.
So, actually, there is not much difference in English either! Both come from Latin 'committere'.