Trying to understand everything about light seems to be a daunting task. But if your up to the challenge go read this: http://www.aquabotanic.com/lightcompare.htm either it will answer most of your questions or you'll just decide not to worry about it any more 
Plants do see light differently than humans. PAR and PUR are discussed in that link and can be thought of the brightness of the lights that the plants see, where lux and lumens are the brightness of the light that we humans see. The problem is that pretty much all lights are measured by lumens and very few are measured in anything thats related to plants. Some have measured lights but I have only found good info on metal hallide in that respect. And the little tiny spectral graphs on the packaging of most lights arent really much to go by, often more a marketing creation than scientefic data.
BTW, that link doesnt really show the photosynthetic responses of plants so here are a couple graphs I often show when these questions come up:
Plants do see light differently than humans. PAR and PUR are discussed in that link and can be thought of the brightness of the lights that the plants see, where lux and lumens are the brightness of the light that we humans see. The problem is that pretty much all lights are measured by lumens and very few are measured in anything thats related to plants. Some have measured lights but I have only found good info on metal hallide in that respect. And the little tiny spectral graphs on the packaging of most lights arent really much to go by, often more a marketing creation than scientefic data.
BTW, that link doesnt really show the photosynthetic responses of plants so here are a couple graphs I often show when these questions come up:
