Nanonancy; There is more that you need to do. because you have a small video card, lower your desktop and game resolution to 1920x1080 or lower. Although an 8GB can render UHD the frame rate drops mostly because you are low on memory. Optimizing your graphics so that your textures are lower than 4k will also greatly improve and lower the risk of that annoying warning. btw many 8GB video cards also have another issue, One, they do not support Hardware Ray Tracing, and two; they bog down when rendering shadows.
The Nanite feature helps a lot, but some assets freak out with Nanite so test each mesh and view it when working with Nanite. Animations such as auto wind on your trees hog video memory. if you have a weather system, use that for the wind animation instead of the built-in animation of the trees. That improves performance and lowers memory usage. The plus side is that it will look more realistic with the trees moving only when there is wind.