Hello,
If you want to have all the images squared then you need to upload squared images from the very beginning or use crop. There is no other way because the width of the images changes depending on the device width and custom height is static. So, unfortunately. You can try to look for third-party plugins for these purposes but there is no option in the theme to make all the images the same height/width, for example https://wordpress.org/plugins/smart-image-resize/ or similar.
I added below code to child theme style.css to fix the sale label issue
.woocommerce ul.products li.product .onsale, .woocommerce span.onsale {
z-index: 2;
}
Check now.
Regards