libFuzzer is more suited to fuzzing a single method, while AFL gives you a little more freedom when deciding how to fuzz your code.
This is a nice initial look at libFuzzer: https://github.com/google/fuzzer-test-suite/blob/master/tuto...
And here are a couple of my favourite AFL tutorials:
- https://fuzzing-project.org/tutorial3.html
- https://github.com/ThalesIgnite/afl-training
Happy to answer any questions!