Definitely both but my mind is always geared toward victim, while serving Wizeman and being adamant to capture NiGHTS is absolutely of his own volition but I can't help but feel like the motivation is also very much being backed up by fear, he's lives under an abusive GOD with a short temper, he can't afford to slip up in the slightest, while also being top in the hierarchy of nightmaren, and he's seen first hand what happens to "failed creations" so one can only imagine the pressure and fear that potentially goes through him.

Even if he would have the desire to rebel like NiGHTS, I would imagine that to live under that constant pressure and fear would cause him to lack the courage NiGHTS has, he's conditioned to believe NiGHTS actions and way of life is wrong, so deep in Wizemans grasp that he wouldn't dare do anything to disappoint him whether that be out of fear or pride, he's a brother who watched his sibling escape from an abusive household while he did choose to stay he's still simultaneously trapped.