Should I allow users to edit/remove products during checkout in the ‘Order Summary’ section?

Note that our products are live online courses, and registration for each course can be upgraded to include additional access add-ons and/or physical copies of the course, etc.

Currently, we have implemented a "remove" link that removes an item from a user's cart once clicked as well as an "edit" link that shows a pop-up that allows customers to edit their add-ons for a course during checkout.

I wonder if adding an "Edit Cart" link above the section that takes the user to our Cart page (outside of checkout flow) to make any changes (edit or remove courses) in their cart. They could then click "Checkout" from there.

I've seen it done both ways, but think it might be a better experience (and best practice??) if we do not allow any changes on the checkout page.

Anyone have any data to share on user experience impact or any best practices to share? I've attached some example mockups below.

Thanks!