yes, yes, and yes! completely agree.If you can manage ventilation and temperature, more light is always going to get better yield. How much better depends on a lot of things, including pot size, space, genetics, and how well you manage the plants' other necessities like nutes, water, oxygen and co2. Keep costs of electricity in mind too. 400w is a big difference over time for the cost of your grow, and if you only have room for a couple of small plants it might not be worth it.