Capital One offers several families of cash back cards: Quicksilver, Savor, and Spark. The Quicksilver cards cash back at a flat-rate of 1.5% back, the Savor cards earn bonus cash back on dining, entertainment, grocery, and streaming, and the Spark business cards earn flat-rate cash back at various rates.
Cash back earned with Capital One's cash back credit cards cannot be converted into rewards with other partners, but they can be converted into Capital One miles if you have an eligible Venture Rewards or Spark Rewards credit card. This will benefit you if you want to maximize your rewards towards travel redemptions.
You can benefit from this by pairing the Capital One Savor or Capital One SavorOne Card with just about any Capital One miles credit card. Use the Savor cards to earn bonus rewards on dining, entertainment, grocery, and streaming and use a Venture Rewards or Spark Rewards credit card to earn rewards at a flat rate across all other purchases.