Swapping out the file does work on 126. Guest checkout still needs to be ON for the buttons to show on the checkout page , but I think that is okay. Admin just needs to decide if they want guests or not, then the payment buttons show up correctly.
I do suggest that this should be stated in the docs you need to add the info that Guest Checkout set to OFF will not show the PayPal Express on Checkout Page .
Thanks for working on this.
Lee