Documentation
Which one you want comes down to a single question: where does the website live?
On Battle Ready Tech
Build a signed package that runs inside a Battle Ready Tech store. New pages, new behaviour, a closed runtime contract, and permissions the store owner approves before anything runs.
Publish it to the marketplace, or hand over a private install link.
Somewhere else
Keep the website you already have. Put your Battle Ready Tech products, class and range schedules, and a working cart onto pages you control, on any platform you can add HTML to.
One script tag and one empty element. WordPress has a plugin that does it for you.
Reading these needs a Battle Ready Tech account. Choosing between the two does not.
Not sure yet
If the storefront is served by Battle Ready Tech, an extension changes it from the inside, and embedding would only put the store next to itself. If the site is WordPress, Shopify, Wix, Squarespace, Magento or anything else, an extension has nothing to install into and embedding is the path.
Both at once is normal: a Battle Ready Tech store running extensions, and the same products embedded in a separate marketing site hosted elsewhere.