Just land or don't land is no decision. Similarly On approach means nothing. How much time it will take to land and bring the aircraft to full stop and attend to the engine will decide your actions. If you are on final Approach and less than a minute to touch down that will be less than 500ft you can go ahead and land do the drill on ground. But if you are above 1000ft then you must at least secure the engine. If the fire is gunuine then it's time critical. Landing without securing cannot be from any height.