Flaked Barley is far better than Carapils, but there definitely can be a detrimental flavor effect and clarity reduction if the content is too high. Most people would not notice the flavor effect at low levels, but unfortunately through my brewing trials, I've sensitized myself to it. That is why I recommended no more than 1/2 percent. That should be fine in a BW, but might need a slight reduction in beers with less flavor to mask the flaked barley flavor.
Oatmeal is somewhat effective too, but not as effective as flaked barley. Oatmeal contributes oils that contribute to mouthfeel, but reduce head.