Hi John,
You’re correct that there’s no “product or services” catalog in Insightly (although, apparently it’s in the pipeline for development this year)
You’re also correct about “categories,” however. You can create these categories in the back-end, then whenever you add a new opportunity you can assign one. Insightly allows you to filter by category, so you can effectively sort your sales opportunities by product. Leads work the same way.
Hope this helps!
Jeremy