Custom header or footer components and the commerce custom layout
Key Takeaway
To show a custom header or footer on an LWR B2B store page, override the page's default theme layout in Experience Builder and select "Commerce Custom Layout".
B2B stores created with the LWR template include responsive header and footer components by default. A developer can build a custom header or footer as a Lightning web component instead. The custom component needs a page layout that leaves room for it, so you assign Commerce Custom Layout to each page where you want it.
What Commerce Custom Layout gives a page
Because those sections start blank, the custom header and footer show in place of the standard ones.
Unlike Commerce Custom Layout, the My Account theme layout gives persistent navigation on the left, with page content on the right. Its menu links appear on all pages that use that layout.