Converting from larger to smaller wire gauge
I am finishing an area in the back of my garage where there are existing washer dryer hookups to create a laundry room with access from inside of the house. My question is about wiring four ceiling recessed cans(60W bulb each). I have 12/2 romex running from an existing outlet in the adjacent dining room- which is the first device on this circuit- into a 2 gang 32 cu inch box where 2 wall switches for the ceiling lights will be wired.This will also power 2 new laundry room outlets and 1 additional existing dining room outlet. First can I have this many devices on this 20A circuit? Second, can I change the wire gauge to 14 gauge to the ceiling cans using 14/3 to create 2 circuits or do I need to use 12/3? Also is it okay to use 3 conductors to create the two circuits for the ceiling lights?