The real difference
Gold-rate apps change prices. A jewelry POS runs the trade.
Shopify’s answer to gold pricing is an app from its store. Apps such as GPE Live Gold Price Editor or GoldPricer take the spot rate and recalculate product prices from weight and purity, and some sync those prices to Shopify POS. For a shop that mainly needs prices to follow the rate, that can work.
A jewelry counter needs more than a repriced tag. In Smart Jewelry POS the salesperson can negotiate wastage and making on the bill, the customer ledger keeps gold in grams, vendor ledgers post themselves from deliveries with Labour/Kaat terms, and old gold is appraised and traded in against the sale. None of that is documented as built into Shopify POS.