What road hub makes the least amount of noise
In my experience, the most silent combination has been Shimano freehub and cheap cassette with pinned together cogs. The one I have is XT, but road hubs below Dura-Ace have similar mechanism. A cassette with loose cogs can vibrate more freely and is louder.

Other brands that I have been riding myself or have had the joy of listening on group rides include Campagnolo/Fulcrum, Chris King, Mavic, DT Swiss and so on. All of these have their own distinctive rackets.

As described in comment, completely silent roller clutch hubs have been produced. They have other, more serious problems.