It is possible to optimize 2d game, because i7 6700k using 10-15% and gtx660 2gb using 50-70% in new side scroller 2d project?.
Maby you can try to use Levelstreaming. Create multible Tile Maps and loaded him. On top try to reduce Lights and change the size of your texture lower, if you not making a pixel art styled game.
Sorry for my Bad English. ^^