Well based on your requirement of allowing them to display the catalog checkout page, these options can force the user through the checkout screen.   You are correct where they are controlling the buttons that show up, but if you want them to always go to the checkout page, then removing those two buttons will force them to edit their cart and then have the option to continue shopping or checkout.   Otherwise if they choose order now, then it will add all the items to the cart and order the item.   Proceed to checkout has similar behavior.

I hope this make sense.