Over the years I got quite a few of singing teachers. One of the mantras is singing into the mask. However, some teachers disagree on the fact being nasal is a good thing or not. But this is not the question.
The real question is: can these 2 things (singing in the mask and being nasal) be really separated? I don't think it's possible to do one without the other. What would the physical mechanism be, which allow someone to bring the vibration in the face (mask) but not in the nose. Is it even physically possible?
You can do a simple experiment now. Try first not to sing into the mask (by dropping jaw and tongue completely). You will see that closing the nose with your fingers will create no change in the sound at all.
Now try to sing into the mask (by smiling a little bit and bringing the vibration forward). At this point, if you are really in the mask, you will notice that closing the nose with your fingers will create a slight change in the sound. That means you are nasal.
So, again... is it even possible to really sing into the mask without being nasal?