For or high-fidelity export : There is no substitute for using Revit (or Revit LT) to export to DWG. A 30-day Revit trial is a better investment than 10 hours of cleaning up broken online conversions.
Not a direct "converter," but allows you to open RFA files and take measurements or screenshots without Revit. Rfa To Dwg Online Convert
Revit cannot save natively as a DWG, and AutoCAD cannot open an RFA file natively. You cannot simply change the extension. You need a translator—specifically, an service. For or high-fidelity export : There is no