As long as you're getting the denoise results performed in DxO, you can treat the ICC profile as a simple preference; whatever you like best as your starting point. I admit I don't know how DxO operates and am a little surprised you can see the de-noised image in another editor still in a RAW format, but if it works for you, then great. And, why can't you tag/embed your camera ICC profile into the DNG from DxO. If it's possible and that's what you want, it would seem the optimal way to do it.