In the game, the map is loaded at 99% but uses only half of the memory and the FPS sags. Why is that?

Question

Video cards

Tell me please. In the game at high settings, fps sags, FPS monitor shows that the card is working at 80 - 90%, although it uses only half of the memory. Why is only half of the memory being used? Proc and disks are not loaded, everything is fine, the laptop is not old and powerful enough, it works without problems, during games nothing superfluous overheats and is not loaded.
Intel i7-9
Notebook Lenovo Legion Y540-15IRH
GTX 1660 Ti 6 gb

Answer 1

Why are cpu and gpu not loaded at 100% in games: https://www.youtube.com/watch?v=cbE31KI0kro
Ps what game?

Answer 2

Video memory usage depends on the screen resolution and the specific game. If there is not enough video memory, then, of course, performance drops are possible, but if there is an excess of it, you will not get a performance increase.
FPS drops are possible due to overheating of the video chip, which is most likely for a laptop.
Check, first of all, the temperature of the GPU.