Green isn't the most powerful, it's just more visible to the human eye, you could have a 500mW infrared laser, you could barely see it but it could burn just like any other 500mW laser. Go to youtube and look up infrared laser.
For your other question, it depends on how mucht current you put in the diode, that's why I posted the graph, say if you put 150mA into the diode, it might give 100mW, if you put 250mA it might give 175mW.
Most people here drive they're senkat diodes at 250mA, that way you have a really good burner, and you get a descent life time.
Oh and I don't know everything, I've only been here a couple of months doing some reading. There's a whole bunch of people here who know a lot more than I do. But thanks. ;D