I have a gtx 1650 super. On maps where there is no water, 4 GB is enough, but on sea maps 4 GB of video memory is clearly not enough. When my camera is pointed at the water, my fps drops from 60 to 15-20, when I point the camera at the ground, the fps returns to normal.
As you can see, all 4GB of video memory is full (only on nautical charts).