Hi Mateo, you need a good book to help you with all these questions, for example http://www.charlesdowding.co.uk/product/organic-gardening-the-natural-no-dig-way/
Onions falling over is nothing to do with no dig, its about their life cycle e.g. autumn planted means maturity is near.
Your white onions, v difficult to say without knowing variety, how and when you planted, soil condition.
