Hey Genova,
So overall the texture streaming system, or streamer, is the part of the engine responsible for increasing and decreasing the resolution of each texture. This enables you to have good visual quality while managing the available memory effectively.
When you increase the texture memory pool, you allow for a larger amount of textures to be loaded and streamed in and out of memory. If this pool is too large, or exceeds the VRAM of your GPU, then you can quickly overload your GPU’s memory and cause it to drop in performance. This is why the default is so low, to account for lower end GPUs with less memory.
It also depends on the size of your textures, LODs, Texture Groups, and biases. All of these settings can help you find the correct texture pool or adapt to your current one in case you cannot increase the overall pool size due to hardware limitations.
Cheers,