Which tool should we use?

There seem to be a bazillion options for automatically generating Related Products. Which should you choose?

Start with what's included and work up from there.

In my opinion, Related Product Rules are worthless when compared Live Product Recommendations (included in Adobe Commerce).

Chances are, you will be happy with Product Recommendations.

If you feel the results aren't great (or you use Magento Open Source), try Algolia. We love this tool and have deployed for a number of websites.