I agree and disagree with spookiest, there's a few different ways you increase yield. Lights do have a part to play, but it's not the only thing. Too much light and you can kill your plant. The strain also dictates how much you can yield, because not all strains are the same. Are you going to stay in a small tent, that's also going to effect your yield. Adding co2 will help increase yield. How many times you top can have a positive effect on it well, but again you're limited on space in your tent. How big is your tent?
A 600w led in a 2x4 tent, is pretty big light, usually those lights are for 4x4 tents. Depending on how big the light is, you might want to get a light mover to move the light back and forth, so that way it will cover the whole tent better. If you do it right, one plant will fill that size tent, with no problems. I have a plant vegging right now, if I was too flower in a2x4, and scrog it, it would fill the whole tent. Topping is hard to explain with out pictures or video. If you search this site, you'll see it, or YouTube would be better. But your making the plant grow multiple larger limbs, instead of the single shoot.
