Make sure your run the game on you Nvidia graphics card:
http://sims4.crinrict.com/en/2014/09/graphics-cardintel-chip-dual-systems/
I am running from the Nvidia GPU, it's not so much frame drops and lag, it seems to be loading times especially.
How are the times when you start a new game?
As in deleting my old savegame? Still just as bad.
It could just be that your computer isn't up to the task. Even with SSD it needs other components to function it's best.
If you want to check that, run this:
http://www.systemrequirementslab.com/cyri
