I purchased the Fiat rails after having issues with the Thule offering which damaged my roof rail finish. (info posted somewhere on this 500X forum). Thule refunded me and I bought the cheaper Fiat bars.
The Thule Aero bars were not silent. I suspect the Fiat bars will be just as noisy, possibly worse, possibly better.
If you have any cross car (as opposed to longitudinal) bar, even so called Aero rounded bars then noise will be present and potentially an annoying issue. The alternative is a Ducato van and put the load / bikes / etc in the back of the van.
Neither do I Goodcoin - Mine are the OE ones as seen here (with-out the extra carrier bit(!)). Does not seem to be many images of a 500X with the OE ones fitted - I'll add some images of mine when I can............