Nothing in the cluster will buzz that I'm aware of. More likely something in the A/C system such as debris or a control 'flap' not closing completely. You could try changing around the settings on the CC unit to see if those cause a change.

People have had varying success with replacement clusters. Within the part number there are 'series' of clusters. At the very least you need the one which matches your ECU. This is why most people live with a few bad pixels or have their cluster repaired. You are correct that the cluster is merely a display and the values are generated/stored elsewhere.