Abandoned cart flows typically have a high number of skips due to people failing a flow filter. In the standard abandoned cart setup, the trigger is Started Checkout and there's a flow filter for Placed Order zero times since starting this flow. This means that everyone who starts to check out is added to the flow.

Abandoned cart emails can be considered transactional if they meet certain criteria, such as including information about the customer's abandoned cart and not including any promotional content.

The Add to Cart flow captures browsers who may not make it to the checkout page, while the Started Checkout flow captures those who start a checkout but don't finish it. That way, your customers won't get both flows at the same time :) I hope this helps!