Your page layout isn't the problem
Sitewide conversion is up 61% year over year, apples to apples, so same weeks both years, non-promo windows, and similar spend. It came from rebuilding the pages where we sell, which for us meant product pages, landing pages, collection pages, and the home page.
We barely touched the layouts though. We didn't move things around, where headlines were we just changed what they said, and most of the lift came from the content.
Where the words came from
We pulled a lot of the new copy from customer language, mostly from reviews.
The clearest example is a headline on one of our product pages. The old one was "Why it's the best in the world," the new one is "Why it'll never quit on you," and it beat the old one by 91% in a test.

The other place we looked was brands selling to the same customer as us in different categories, because the way they talked to that customer was compelling to us, and we felt it'd be compelling to our customer too.
A reshoot instead of a redesign
The old images weren't compelling, so we did a reshoot and went back through the selects, and we ended up with more studio shots than before. Instead of doing all the best practices, we made what we found compelling ourselves.
What didn't work
We tried completely new page styles along the way too, fresh landing pages built from scratch, and they didn't do as much as better copy and imagery inside the formats people were already used to. The familiarity seems to help the content land.
How we measured it
We didn't split test the rebuild itself. We straight up shipped it, which is how I think big swings should go out, and we still run headline tests on top of the new pages, which is where the 91% up above came from. The 61% is measured exactly the way I described at the top, and the number still holds.
The time for all of it came from cutting most of our discounting. The hours that used to go into planning promos went into the pages instead.