This is a basket with an optional frontend-user. If no frontend-user is logged-in, the user can choose creating a frontend-user during checkout or buying as a guest.

Read more about checkouts: https://www.coding.ms/documentation/typo3-shop/basketcheckout/checkout

themes.configuration.extension.shop.checkout.onInvoice.active = 1
themes.configuration.extension.shop.checkout.prePayment.active = 0
themes.configuration.extension.shop.checkout.request.active = 0
themes.configuration.extension.shop.checkout.stripe.active = 0
themes.configuration.extension.shop.checkout.payPal.active = 0
themes.configuration.extension.shop.checkout.payPalPlus.active = 0
themes.configuration.extension.shop.checkout.payPalCheckout.active = 0
themes.configuration.extension.shop.checkout.klarna.active = 0
themes.configuration.pages.shop.checkout = 98
themes.configuration.extension.shop.checkout.onInvoice.fields {
    available = firstname, lastname, email, password, privacyProtectionConfirmed, termsConfirmed, disclaimerConfirmed, createFrontendUser
    required  = firstname, lastname, email, password, privacyProtectionConfirmed, termsConfirmed, disclaimerConfirmed
}

Pay attention to the fields. The field createFrontendUser is available but not required. The field password is available and required – but the password field has a special behaviour: It will be only validated if the createFrontendUser checkbox is selected during checkout!

This makes it possible to create a frontend-user during checkout when createFrontendUser is selected or buying as a guest if it's not selected.