I would like to know if there is a way to change the ATC button link on the product page from going to the checkout page to opening up a popup that asks the users if they want to continue shopping or go to the checkout page.
I know for a fact that there is a targeting feature called "On-click" offered by Popupsmart
This feature does exactly the thing that you want it to do, like displaying a popup on a button click. You can check out their free plan as you can try all the features on the free plan. Hope it helps!