1st - virtually zero
2nd - not really
3rd - Volunteering? are you volunteering or trying to get voluntary brownie points by volunteering? If that is the case, then you are not volunteering at all, you are expecting a payoff in the end. And as soon as you get your PR that would be the end of it. ICS has seen 3rd world citizens abuse this time and time again. So if I hit a nerve, just stop now as it's not going to make an iota of difference on your application.
If you are ethnic Vietnamese and not Chinese Vietnamese, save your time and money. It's probably never going to happen. Yes, I'm a little blunt, but I don't believe in sugar coating because too many take that the wrong way. This way you get the unvarnished truth of the matter.
SOME PEOPLE TRY TO TURN BACK THEIR ODOMETERS. NOT ME. I WANT PEOPLE TO KNOW WHY I LOOK THIS WAY. I'VE TRAVELED A LONG WAY, AND SOME OF THE ROADS WEREN'T PAVED. ~ Will Rogers