Okay.. And can you download Nvidia Inspector and CPU-Z .. Play a replay on LFS and do like I do in this screenshot?
As you can see my GPU does NOT run full speed, it's throttled down. 405 Mhz instead of 666 Mhz, also the memory is on 800 Mhz instead of 1800 Mhz. And this, most of the time is the problem nowadays with LFS. You can set GPU on full power in Nvidia control panel but with the risk of getting more noise due to cooling.
This is P5 state by the way, but it has happened to me that it even switches to P8 state (234 Mhz) and then you get this laggy/choppy screen effect to the extreme while FPS can be reported as 'normal' as you described.
There is no complicated way of saying this so I say it the easy way; buy a different laptop which can actually perform. "HD Graphics" is useful for Youtube and that is about it. First three generations do not do anything.