​It is possible for you to apply painters putty onto a flawed area on a drywall surface. Technically the painters putty will adhere to the surface, but painters putty is not intended for use on drywall and will not adhere, or cover damages as well as spackle, or drywall compound will.
Painters putty is intended to be used on plaster surfaces. If you want the best looking finish then use the spackle on the drywall and the painters putty on plaster.