watts are irrelevant for LEDs. Any decent LED manufacturer will provide you with a PAR map which you can use to give you an idea of what to expect in your tank.
If you know what you need, you can save money on your LEDs. For example, I have a 29 gal lit with Fluval Marine and Reef 2.0 with the wifi controller. Many will look down on these and Ill be the first to admit they generate a lot less par and are limited in what they can control compared to better LEDs like Kessils. However, at 3" they produce 385 Par and at 6" 250 PAR, IMO enough for my SPS and the softies and LPS lower in the tank are doing great. They are dominated by 15K white lights which I prefer for day viewing with blue and red to balance growth and color. The blues can be controlled separately with 4 spectrums with 25k temp which makes the colors pop in the evening as I sunset the whites off.
While I would prefer more control over the spectrums other that blue v daylights, the pre-set spectrums from manufacturer took a lot of the guessing game out of the equation for me.
If money was no object, I would have gone with Kessil or another high end brand, however it's not and the Fluvals met my needs for a lot less.
I am not recommending Fluvals, rather than passing along the benefit of doing the research to understand what you want and need in lighting and then shop.
In corals, growth and color are hard to achieve at the same time. The spectrums that will encourage the most photosynthesis will also encourage the brown pigments. Your eyes will lie to you about PAR. Some people prefer the blues for viewing, some whites. Blues can pack a powerful PAR punch and while the tank may look dark, the corals can be bleaching. This is why it's critical to know the PAR levels in the tank.
