Magento is one customizable beast of an eCommerce platform. If you’re willing to brave direct SQL calls to create a product feed (please don’t!) or willing to try some slow plugin to directly send products to Google Shopping, you should consider optimizing the Magento product feed before it goes out to any advertising channels.
Otherwise, you might be missing important keywords like brand, color, size, and other relevant Magento attributes that will be lost when sending the feed to Google Shopping.
The best solution is a feed platform like Feedonomics, that can easily export your Magento feed to Google Shopping, and perform the optimization needed to compete on Google Shopping.