Every product research tool works from public signals: Amazon's sales ranks, a Shopify store's public catalog, the ads running on social platforms. None of them sees a competitor's actual orders, so every sales figure they show is an estimate with blind spots. Restocks look like sales, bundles sold through apps disappear, and an ad with many likes may sell nothing. The useful skill is reading each signal for what it can show. How long an ad has run says more than its engagement. Sales that hold across several weeks say more than a one-day spike. A product only becomes worth testing once demand, supplier cost and delivery time all check out.
Dropship.io vs Minea separates the two research questions: whether a product is selling (store sales estimates) and how it is being marketed (ad intelligence). It also lists where each estimate goes wrong. Monitoring Shopify competitors through products.json shows the data underneath. Most stores publish every product and variant with price and stock status, 250 per page, and a short script can snapshot it and alert on price changes, stock changes and new products. Done politely, that means checking robots.txt, pausing a few seconds between requests and backing off on HTTP 429. For Amazon, reducing PPC ACoS starts from your break-even ACoS, which comes from your margin, and cuts waste weekly from the search term report.
Fulfilment is the other half. AutoDS vs Spocket separates automation (price and stock monitoring, order placement and tracking sync across many suppliers) from sourcing closer to the customer. It includes a per-order margin model that counts refunds, because slow delivery costs more than the shipping difference suggests. Switching to US and EU suppliers covers the move away from long overseas shipping. Helium 10 vs Jungle Scout compares the two main Amazon research suites.