This is Finley from Shopify here. Thanks for reaching out to us!
To clarify, when your customer attempts to checkout, they are met with a page where they need to create an account to proceed with the checkout, like so, is that right?
If so, this can be updated from your Shopify admin > Settings > Checkout > Customer Accounts. From there, you can select one of three options for customer account settings:
1) Accounts are disabled: The customer won't get the option to create an account with you or to log in to their account during the checkout process. They'll need to manually enter their details at checkout.
2) Accounts are optional: The customer can create an account if they wish, however it will not be a required step. If they choose to create an account and log in, their address fields are pre-filled when placing an order
3) Accounts are required: The customer will be required to create an account and log in to checkout. This is common for wholesale or members-only stores. The address fields are pre-filled when the customer places an order on your website.
You'll also notice in the Settings > Checkout page there is an Email marketing section. You can select the Show a sign-up option at checkout option. This is in fact optional, so your customers can choose to opt-out:
Depending on where you're located and your preference for the customer's experience, you may want to enable double opt-in as well.
This means that your customers will need to click a link in an email to confirm that they agree to receive email marketing from your business.
Though you want to make subscribing optional for your customers, for those customers that do want to subscribe, you may find that you're interested in email marketing. If so, we do have a detailed course on Shopify Compass if you'd like some more information.
I do hope I've answered your question however if not, please let me know and I'll be happy to take a closer look.