A slow product page is a closed drawer
Daily checks, alerts when they slip.
Shoppers do not wait for a 4 second hero image. They go back to search. Ecommerce vitals work is not a homepage trophy. It is product, collection, cart.
Product pages
LCP is usually the main image. Size it. Preload it. Do not lazy-load it. Reviews and recommendations can wait.
Collections
INP dies on filter clicks. CLS dies on images without dimensions. Fix templates, not one-off pages.
Cart and checkout
Third-party payment and upsell scripts add long tasks. Measure INP. If you cannot measure every checkout step, measure cart.
Sales and campaigns
A promo banner that inserts at the top of every page is a classic CLS event. Monitor through the sale, not only after it.
FAQ
Is a faster theme enough?
A faster theme helps until you install the same ten apps. Measure the live shop.
Should I use the origin CrUX or URL-level?
URL-level for the templates you care about, when traffic is high enough. Origin as a backup.