If you want the bars significantly lower you can "flip" the stem over to reduce it's rise.

Also to lower the stem you can, and should, remove one spacer from under the stem and place it on top. Then install the top cap on top of that spacer, snug it's bolt to adjust the headset preload, center the stem over the front wheel and tighten the stem clamp bolts. More than one spacer's worth of change will probably require shortening the steerer tube

And, yes, current threadless stems are significantly lighter than their quill predecessors.