I have Product A that sells on Amazon USA and UK.
I have a Shopify store where I want to offer the product for sale. If the user is in USA, I would like to show them USD price fulfil the product from Amazon USA. If the user is in UK, then show in GBP and fulfil from Amazon UK.
Do I need 2 stores for this or can I do it with one store?
If you want to sell your products separately from Amazon USA and UK, it's better you run two different stores on Shopify. It would provide you the flexibility to control differences of currencies, prices, shipping costs, and stock capabilities.
Among the two different Shopify stores, with the multi-locations settings, you could auto redirect your visitors to correct regional shop URLs using IP geo location technology. For example, Geo Targetly, specifically, Geo Redirect tool. It can detect your visitor locations based on IP and auto direct them. You can easily set up geo location segments, and redirecting rules within a few steps. No code is necessary.
Hope it helps!