API integration use case design

[Sensorpro]

Hi,

I am writing integration to Shopify and I have a need to use unauthenticated access to update customer data from an external system and load all customers into the external system from Shopify. 

After the initial load is executed I can use a web hook to keep the contacts synchronized. But there will ne a need for an initial load.

These actions happen from a back end process so no one will be logged into the store when this process runs. 

So 99% of my interactions will be customer based.

I was hoping to just use the Admin API but it looks like I need to use the Storefront api and to do this I need to convert my public application to a sales channel for unauthenticated access. My queries are:

1. Just confirm I have to use Storefront api for unauthenticated access with a sales channel app.

2. I was experimenting with storefront graphIQL and I could not  find a way to get a list of all contacts, it looks like the customer object has a required parameter customer accesstoken

    is this exposed through the storefront api?

Thanks for you help