We already have a store that's built on Angular with a custom-built order management system. We're looking to migrate to Shopify but not sure what the best route would be. What we have is basically a dynamic JS heavy image editor which allows customers to personalise merchandise with a live-view showing them the changes. Then they hit "add to cart". At that point, we'd want to send the product details to Shopify's cart and manage the checkout experience and order management in Shopify instead of doing this in our own backend.