Freelancer:
Nacho1993
Rejected
Ella - Shopify theme
I think that this is a great template for your idea, it has tons of features and will suit almost all of your needs https://themeforest.net/item/ella-responsive-shopify-template/9691007 here you can see a demo of one of the implementations using parallax https://new-ella.myshopify.com/?fts=0