Ultimate Special Offers handles in-cart % discounts and the cart callout, while the compare-at price just uses Shopify’s native sale/compare setup. Used this combo on a client store recently, cleanest way to mirror the Coach Outlet layout.
One alternative that worked well is shifting that “extra value” into a bundle-based incentive instead. You keep the compare-at + sale price on the PDP, and instead of applying another discount in the cart, the cart callout highlights the bundle savings. Cleaner implementation, no conflicts with other automatic discounts, and the customer still perceives an “extra deal” when they add to cart.
Functionally it hits the same psychology without juggling multiple discount layers.