Products image size can be changed only via Customizer > Woocommerce > Product Images. Don’t use hard crop if you don’t want to crop images. Please read this article – https://docs.woocommerce.com/document/fixing-blurry-product-images/
We would recommend to use a graphics editor and prepare product images (make them the same size) before uploading it to your media gallery, then your grid will look much better.
