Turn on one app embed in the theme editor, with no code changes. It preloads the main product, collection or article image, loads the next page while shoppers hover (Chrome and Edge), lazy loads images further down the page and can hold back scripts you list, like chat or review widgets, until the first interaction. Add ?weedit_speed=debug to any page to see Core Web Vitals and suggested fixes. Cart, checkout and account pages are always excluded, and the app needs no access to store data.