Click on the Sticky Add to Cart button behaves the same as if the regular Add to Cart button was clicked. So there should be no issues with the Sticky ATC Bar/Button.

Please note that Skip to Checkout features cannot be used in this case.

Quick Buy Button doesn't support subscription apps yet, unfortunately.

Sticky Cart should link to the cart page, not checkout since subscription apps require that users go to checkout from the cart page.

Sticky Checkout Bar/Button behaves the same as if the regular Checkout button was clicked. So there should be no issues with the Sticky Checkout Bar/Button.