Yes, its possible to sync data between ERPNext and Shopify. Now you simply have to install the Shopify app using the ERPNext app installer. It’s seamless. Once you do that you’ll be able to add the shopify settings under the “Shopify Settings” page. You can sync customers, Sales orders, Sales invoices, Payment entries. More on this here.
The Quickbooks to ERPNext migration tool has been WIP for a long time. We’ll have an update on the same for you in some time. For urgent requirement you can use the excel data imports, which definitely are free.