I am trying to capture this windfall but Shopify is not good for this task.
They charge per store so I am limited to just having one store which is not good for niche work - exploration and discovery.
I would probably develop a framework and do free gatsbyjs/netlify static sites that link back to a centralized payment processor service
For an use case like yours, the 20+ websites are more akin to microsites focused on a subset of products but still mapped to one single catalog and ecommerce store.
Even with ShopifyPlus multi store support each store has its own catalog, and completely seperate for integrations, transactions, etc.
We can make subaccount in stripe, so it's easy to specific different subaccount for different product.
While WooCommerce is there but still we need to setup wordpress blog and multiple other things.