I am using the Vantage theme for my website and there are some changes that I have been trying to do to the CSS.
There is a section in the Style.css that says "/* This will override anything from WooCommerce core CSS */"
I have found this not to be true. For example if I want to add padding to a product box I Inspect the element on Google Chrome and see that it is done through the WooCommerce CSS. I make sure I get the correct code and then paste it into the correct section in the Style.css changing the padding, it does not override the Woo Commerce styling.