lumens are a rating of the light coming off the bulb but I generally worry more about the PAR rating of the bulb cause that's what makes the plant grow...if a bulb produces 100,000 lumens but only 10k lumens are in the right spectrum it's still not as good as a 50,000 lumen bulb with 20k lumens in the right spectrum or PAR...

I'd go with floro for veg and hps for flower the size and type of bulb you get depends on the type of grow you are gonna have...sativa/indica take different light levels too sativa like much more and hotter temps generally