Your NIW is not sponsored by any specific employer. Sure you can change job anytime, the only requirement is that you stay on the career path outlined in your I-140 material.
If your approved I-140 is EB3 or EB2-1, then file I-485 now. You can change job after 180 days of I-485, but the new job has to be a similar position.
If your approved I-140 is EB3 or EB2-1, then file I-485 now. You can change job after 180 days of I-485, but the new job has to be a similar position.