Humans can be both combatant and non-combatant. Those that have powers and are combatants generally channel their powers through some object of theirs or have powers that compliment their personalities. For example Chad (Sado) is a tough person and fights to protect the people he cares about and this causes his powers to be defensive at first and eventual become offensive.
Human Combatants all have different powers and have them generally develop because of continued ex-poser to the raiatsu of a strong Soul Reaper. The only exceptions to this are Quincy as they all have similar powers to each other and are born with their powers.