SCR, is A CTR with a side charging handle instead of a traditional Charging handle, not needed (although could be handy but requires practice)
PSC, Upper reciever that has both a side charging handle and traditional charging handle, mated to a JP-15 lower.
CTR, Billet Upper and Lower. JP's flagship for Competition rifles.
JP-15, Forged Upper and lower, more traditional AR-15 look.
Go with the 18inch Mid contour or Light Contour Barrel. JP triggers are 1 stage, but that's all you need really. Go Low mass. Heat sink is a big NO. XL hand gaurds are nice but not needed, but all my rifles run a 15"+ handgaurd. If your looking for the "lightest" setup go with the JP-15, it will also cost you $700 less then the SCR.
Out the door, with XL Handguard and the other options you wanted(minus the heatsink) that you posted + a 18inch barrel, a JP-15 will run you over $2000, Can't beat that with a stick.
Why no to the heat sink? I ask because I have a rifle on order and I included it. Guess I should have searched first.