Klaviyo now lets brands run up to four RFM models (recency, frequency and monetary value: how recently, how often and how much a customer buys). Each model can use its own conversion metric and thresholds, so you can score customers separately for each product category. Klaviyo's example is a shopper who buys apparel often but has stopped buying footwear: one blended score hides that, a footwear model shows it.
One RFM score across a whole catalogue lies to you. Your best apparel customer can be lapsed on shoes, and a blended model will still call her a champion.
Category models give you a list of people who already trust you and have stopped buying one thing. That is the cheapest revenue in the account, and it is perfect for Q4.
Check you have the right plan and enough order data before you build. Then keep the message specific: a new running shoe, not a sitewide discount.