Fast and Frugal heuristics can be descriptive (meaning human beings naturally use them at some level) or prescriptive (here are some good heuristics you can learn to use). Heuristics in Heuristics and Biases are only descriptive.

The Heuristics and Biases theorists would never suggest someone should try to "use" one of their heuristics, nor probably could you even if you tried. You could not intentionally reproduce the pattern of cognitive biases that their heuristics allegedly cause, many appear to be irretrievably outside of conscious awareness or control. For that matter, they often appear to be nearly impossible to stop using even if you wanted to.

Fast and Frugal heuristics, however, you can learn and use intentionally. The Fast and Frugal theorists generally don't suggest that it would be difficult to stop using their heuristics should you be aware of them and have the desire to. Descriptive heuristics may even be discoverable via introspection.

Heuristics in Heuristics and biases are defined as having negative side effects. There are no heuristics in H&B that aren't revealed via errors. Heuristics in H&B are presumed to be either needed by some necessary efficiency or could be an evolutionary quirk like the blind spot in your eye. Fast and Frugal heuristics do not require negative side effects and are usually not described with any. Descriptive F&F heuristics aren't evolutionary quirks. Heuristics in F&F are defined as being a helpful efficiency gain.

So they are mutually exclusive in some properties, besides the obvious that Fast and Frugal heuristics are "good" while heuristics as in Heuristics and biases are "bad".