Hello,
The difference is because your Shop page is currently configured to display product categories along with the products, while the demo Shop page displays products only.
To make it look like the demo, please navigate to:
Appearance > Customize > WooCommerce > Product Catalog
Under Shop page displays, select “Show products” only.
This will remove the category display from the Shop page and show only the products, similar to the demo.
Regarding the product images, I see the product image has the same size on your site in archive pages.
Best Regards
.
