The plugin cannot modify any snippets created by WooCommerce. However you can completely deactivate the generation of snippets created from it. Then you can re-create the products snippet on your own. In version 2.2 the plugin has a partical WooCommerce support. So it might be that you get in trouble by creating snippets for variable products with multiple prices, for example.
Yes, there is a partial support for it. However please note that WooCommerce creates Rich Snippets on its own. My plugin gives you the opportunity to remove those snippets so that you can create your own product snippets.
This is what has changed during the latest updates of the SNIP plugin:
Since version 2.2. you can now add things like ‘offers’ directly when creating snippets. The data then comes from the WooCommerce products directly.
Since 2.5.0 it’s possible to add product attributes to snippets as well.