I'd export to whatever the project was originally worked at. For instance, if the project is 44/24, export a riff wav to 44/24. CW isn't highly regarded for it's conversion capabilities in comparison to the high quality tools most mastering facilities employ. Let the folks w/ the better equipment make those conversions when needed.
That said, IF you are doing your own burning, you're best served by 44/16 riff wav.
Again, I'd export out of CW at the project spec, but convert in Sound Forge or Wavelab afterwards.
If you don't have those programs, then exporting riff wav at 44/16 w/in CW is the way to go.
Best,
Kev.