my good sir or lady,

1) it's impossible to say what would be the most efficient lighting to grow because you need to provide us with measurements of your available space. if, for example, you have a closet that is 4'x4'x7', then that is a small room and you should head straightaway to the hydro store and get yourself an HID light, between 400-1000W. Conversely, if your space is much smaller, go with something far less powerful. how many plants do you plan on growing? if only a few, then a 400 should be sufficient (assuming your space can support it). if growing more than a few, and you want to maximize the space, go with 1000. you simply don't provide enough information. needless to say, your plants will use up almost whatever quantity of light you provide them with. lumens to yield ratio, 400W wins the day. however, if you can afford the extra cash, plus the added ventilation, and wish to maximize yield in a given space, then 1000 wins the day.

2) seedling to bud in 8 weeks = impossible. flowering alone takes 8 weeks, almost all the time, hardly any exceptions. that said, if you plan on growing from seeds, then you'd probably want to let them veg for a long time too, to make the most out of the long time it takes for seeds to germinate and then reach maturity. now we're looking at MINIMUM 8 weeks for flower + 3 weeks for veg + 1 week for germination = 12 weeks on your plate, more likely reaching 13 weeks. best of luck.