All releases of the Micro-Trains 123 body style "TBOX" car (I somewhat incorrectly abbreviate it since "National Steel Car 60 Foot High-Cube Exterior Post Double Plug Door Boxcar" is a mouthful) have come with metal wheels. The forthcoming PS-2 covered hopper from them is also listed as coming with metal wheels.
None of the above. My MT OEM plastic wheelsets are smooth, quiet and I don't have to spend any extra money to "upgrade" (?) them. Why would I? (that said, I'm also happy with the OEM close coupling truck mounted couplers - call me a dinosaur who just enjoys running trains)
Only my HO steam engines have metal wheels. I don't understand the need for them otherwise. Except if you need an electrical source in passenger and caboose.
Metal wheels help keep the track much cleaner. They aren't noticeably louder than the MT Delerin wheels. I hope Fox Valley gets the wheels in production again soon.