What fields are mandatory for CC payments?

I’m selling only digital products, so don’t need address fields at all. I just need an email address for confirmation & link delivery.

To make it as simple as possible for customers, I want to have only mandatory fields for CC processing displayed in the checkout process, but I’m not sure which they are.

In testing, a CC transaction will go through successfully with only Country/State/Postcode, but when I try and hide the street address and city fields, I get an error (even though those fields were empty when it processed successfully).

The error in the log is always
04-30-2020 @ 06:56:12 – Square.js Response:
Array
(
[code] => EXPECTED_STRING
[type] => INVALID_REQUEST_ERROR
[message] => Expected a string value.: verification_details.billing_contact.address_lines[0]
)

OR

billing_contact.address_lines[1]

(I made all fields optional for this testing, and removed the fields via functions as per woocommerce info here, then with WooCommerce Checkout Field Editor plugin bec I couldn't get the first to work but got the same result)

So my questions please:
1. What are the mandatory fields passed through for CC processing?
2. If those address fields aren't mandatory (which it seems they aren't since I could buy something with them left empty), is there a trick to removing/hiding the non-mandatory fields that I'm not understanding?

Thanks.