Shopify fixes your URL structure. Products live at /products/, collections at /collections/, static pages at /pages/, and blog posts under /blogs/. You cannot create arbitrary root-level pages from the admin. So when you plan SEO content beyond your catalog — buying guides, ingredient explainers, comparison pages — there are three realistic places it can live.
First, the blog that ships with every Shopify store. Second, a separate site on a subdomain such as guides.yourstore.com, running any CMS you like. Third, pages served by an app on your own domain through Shopify's App Proxy, which forwards requests under a prefix like /apps, /a, /tools, or /community to the app's server and returns the response on your storefront's URL.
This choice matters more than most theme decisions, because it sets three things at once: which domain accumulates the authority your content earns, how many pages you can realistically publish and keep current, and whether you can measure any of it. Each option's sales pitch tends to skip its own costs, so this comparison names them for all three.