I believe it helps a lot with MX switches. Unless you have silent reds/blacks, you will be dealing with bottom-out and upstroke noise, and anything you can do to dampen that is worth doing, IMO.
It isn't nearly as necessary with Topre switches which are soft on bottoming out and silent on the upstroke if you install silencing rings (which I highly recommend). So a NovaTouch doesn't need any sound dampening inside the case, IMO. I don't think an aluminum case will make any difference in that regard, but I won't know for sure until I get mine.