In general, FarApp does not sync customers to NetSuite unless the customer is affiliated with an order that is synced. There are some connectors - like Magento - where this feature can be implemented as an add-on. Customers can be set up to sync without an order when the add-on is enabled. You can see if your connector supports this feature by viewing the connector details on FarApp's product page - https://www.farapp.com/products/.
To enable an add-on please reach out to FarApp by submitting a support ticket - https://support.farapp.com/hc/en-us/requests/new.