We rebuild the page closest to your sale and run it against your current one on your own live traffic. The scoreboard is revenue per visitor, not a dashboard metric.
Usually the product page, because that is where the money is decided. One page, rebuilt properly, rather than a list of small opinions.
Old page and new page run at the same time on your traffic, so seasonality and ad spend hit both equally. The result decides.
Two or three tests a month after the rebuild, each one judged the same way, so the store keeps moving on evidence.
It suits Shopify and direct to consumer brands with enough traffic for a test to reach a clear answer in weeks rather than months.