Looking at swapping Kitchen (10 bulbs/5 light units) and Garage (12 bulbs/6 light units). Read so much online info I am more confused. Some LED bulbs can go straight into existing lights w/ballasts intact. Other LED bulbs require cutting ballast wires and wiring power direct to existing tombstones. Variations on these add more options. What is best route? Saves most KW's? What is cost effective? What brands to use? or avoid? Also, current bulbs are T12 but told T8 uses same tombstones so not an issue, right? Thanks in advance.