I hope I solved the problem, but I'll check on other games.
For the Youtube problem: in Chrome disable hardware acceleration in the preferences under more preferences.
For now I don't experience any lag so far.
For the games : in Nvidia settings under "Set Physx configuration" set the Video card u own and not "Auto-select".
I Tried it on F1 2013, where there I had lag just after 5-10 seconds of gameplay with my gamepad, but now I can actually play the game. Hope it fixes in all other games.