[sonick]

Semi not related as this is related to fat cutting not weight loss, Re: Walking vs Running, technically if one is trying to lose fat (i.e. cut), lower intensity steady state training (light jog/speed walking) is better for fat loss and muscle maintenance vs. higher intensity workouts like running.

If you are looking to strengthen your cardio, then running and HIIT is more effective.

For OP, if you do add strength training it should be higher intensity whole body movements (squats, cleans, etc.), vs simply curls and bench press. Regardless, your diet is probably going to be the main factor in this goal, supplemented by whatever exercise you choose to do.