Checkout is one of the major concerns of any e-commerce store as it could be a game changer. I have read too many articles talking about best one page checkout module for Prestashop and found this one https://www.quora.com/Which-one-is-the-best-One-page-checkout-in-Prestashop very helpful. If you are also concern about your e-commerce store then you should read this article at least once.