Foreword placement

Should I do the warmup exercises and sing with a foreword placement (singing in the mask) and is it bad or good for the voice.

also is there supposed to be any sound coming out of the nose 

Hi, George! Some singers and teachers talk a lot about forward placement - and to them, it's the ideal. My view is that "forward placement" is helpful when you want a brighter, more "forward" tone, but that's not always the case. If you like the sound of your voice and feel good when you're "placing it forward" or "in the mask", then great!

And as for nasal resonance, it really doesn't impact most of the sounds we make, with the exception of nasalized consonants like M and N. 

So for example for the ieaou vowel exercise. Is there nasal resonance or is it with a lifted soft palate 

I'd say for a vowel exercise, your palate should be slightly lifted (to avoid an overly nasal tone), but it doesn't need to be lifted a lot unless you're about to sing some classical music!