Hello,
1. If I catch your idea, you can find this option in the Theme Settigns > Performance > Lazy Loading > Upload custom placeholder image – adds custom image placeholder that will be used before the original image will be loaded.
Let me give you a piece of advice, if you add custom JS, add to the Theme Settings > Custom JS, if you add PHP, add to the functions.php of the child theme and update the parent, in this case, your customization would never be lost.
1. You can set the counter for each product and show it in the grid. If you want to add the counter to the category, create HTML block, add the counter element, and then add this HTML block to the category description: https://xtemos.com/docs/woodmart/html-blocks-2/#cat_att_tag
Best Regards