Nope we can’t based on the information we have but that reminded me this thread Laptop Nvidia Gpu frequency locked to 33mhz after unplugging from power - #2 by omano which is still not closed (the guy didn’t connect to forum since long time).
I don’t own a laptop I only have one under my eyes from time to time for friends and family, so I’m not sure how to troubleshoot your issue.
First explain in more details the exact issues you have.
“constant lag and unability to watch HD videos” is pretty vague (what is lag for you, where, how to reproduce? what type of HD videos, how do you play it?).
Maybe check Nvidia Settings application to see if you can gather relevant information too.
PS: if your CPU is supposed to have an integrated video chip (which in theory it has?), where is it? Did you disable it in the BIOS?