The Integration Section in Azure Architecture Center is a good starting point with a couple of architectures discussed and for best practices, the docs on API Design and API Implementation cover many aspects to consider.
UPDATE
I'm unaware of any doc that lists any recommendations as such but here are some things you could consider, I believe might help.
Firstly, a product primarily provides a container for a subset of APIs with an extra policy layer and subscription support. And with that in mind, some ways to leverage products could be
- Pricing Tier
The product policy scope could be used for tier specific subscription keys and access restrictions like rate limit and quotas. - Audience
A product could be used to expose a subset of APIs depending on the audience like internal or external consumers. Or you could have client specific products like for example a product for desktop users, mobile users, etc. (for APIs that are used directly by end-users in a consumer application). - Domain Grouped
APIs could be grouped based on their domain like sales, HR, etc. for example