The Warpies most often develop from young humans, from unborn babies to children. A few adult or young adult Warpies have been shown, such as James Christian. It was stated that no Warpies in Cloud Nine were adults.
The Warpies possess various powers, much like mutants or Inhumans. The most known and feared power is spontaneous and uncontrollable explosions, causing the death of the individual and all beings in proximity to him, but many other powers are known.
The Warpies often have no control of their powers, as many of them are newborn babies. Also, their powers are very strong and eventually kill them before they reach maturity.
For a full list of Warpies, see here.