Lumens are not relevant to plant photosynthesis although with specific wavelengths it can give SOME comparison among those specific lights themselves. The idea is that, for instance, a light that produces all wavelengths only produces 5% of the light needed for plants, which would make it ROUGHLY equal to an LED light that is 20x times weaker. This is rough because so many other factors are at play such as which chlorophyll are we talking about and at what stage of plant growth, etc, etc, etc.

Blue and red are the most important. For leafy greens like vegetables, get a mostly blue one. A lot of science still needs to be done to determine exactly what wavelengths are best, and it will likely vary between plants and even strains. The best thing to do is to save the seed from the best growers for your specific lights and use those the next season or clone the ones that did best. Farmers have done this for years (although the industry has bullied them into buying seed rather than using their own). Anyway, good luck and please keep us posted!