Anyway nvidia thingy is a failure , the reason why some issues occurs is that the switchable graphics still writes to the internal GPU framebuffer which is stored in RAM. Basically both the graphics card are working when nvidia turned on. It does not switch like AMDs one or how apple does it

AMDs - is between on the go or power. Basically when you're on battery , you're forced to use onboard GPU. on AC , you get the faster graphics processor
Nvidia - Basically best in both worlds. It loads on demand when it sees you're using demanding application it switches on the dedicated GPU. But there is disadvantage , the onboard GPU is kept running when dedicated GPU is turned on. While on battery , it can consume even more power , and when you switch it has to remove framebuffer from nvidia card and back to intel. Basically when you switch , nvidia uses intel's "memory" instead. Basically it would be like having 2 RAMs (1GB for nvidia , 288MB or whatever Intel gives to their video card. So when you load games , the processing is done in "nvidia card" and its transferred to Intels onboard GPU memory and Intel feeds this information to the display. Basically intel card as acts a middle man
Apples Solution - similar to Nvidias except that OS handles (notice , apples solution does not work on windows) the whole thing. when onboard GPU is activated , the dedicated is shut off. when a user runs demanding application , contents of the framebuffer is transfered to the dedicatd memory and nvidia has full control , intel gpu is shut off.


This gives you the answer why it flickers for nvidia optimus user. Bear in mind if you activate nvidia gpu on battery , its going to suck even more battery life as both intel and nvidia cards are turned on