I’m a nose breather too. And I don’t think exhaling through your nose has anything to do with a leaking mask. Sometimes the bubbles will find their way into my hood and make me slightly positive until the air leaks out. But it shouldn’t let air in. I probably breathe out through my nose 50% of my breaths with no water entering. I think it’s more likely you have hair getting under the skirt. My wife has long hair and always seems to have that issue. Or possibly the edge of your hood. I like frameless masks for a better fit.
As for purge vs. non-purge. I’ve never used a purge mask, but many a proclaimed expert have told me not to use them for two reasons. 1. It’s hard to pinch your nose for equalizing. 2. It’s a plastic part that can fail or get smashed in your bag and broken. I also figure if they worked well...everyone would be using them right?
Hope this helps.