Redshift has the capability of "out of core" rendering which means that if a GPU runs out of memory (because of too many polygons or textures in the scene), it will use the system's memory instead.
In some situations this can come at a performance cost so we typically recommend using GPUs with as much VRAM as you can afford in order to minimize the performance impact.
Certain types of data (like textures) actually work very well with out-of-core rendering. This means that even if your scene uses tens of 4K or 8K textures (i.e. several GB worth of data), you can still expect great rendering performance!
Certain types of scene assets are not handled by Redshift's "out of core" technology. These include sprite node textures as well as volume grids (such as VDB files).
If a scene uses too many (or too high-resolution) sprite nodes or volume grids, these might not fit in the GPU's memory and rendering might be aborted.