Native vs Upscaled Resolution
Resolution is both an image-quality choice and a major part of the rendering workload.
Native rendering
At native resolution, the game renders its image at the target display resolution before presentation. This can provide a straightforward image but may require substantial GPU work.
Upscaled rendering
With upscaling, the game renders internally below the target resolution and reconstructs the image. The lower internal workload can improve GPU-limited performance.
The trade-off
Lower internal resolution can reduce fine detail or introduce reconstruction artefacts depending on the method and mode. Higher-quality modes usually preserve more detail at a higher performance cost.
How to choose
If native performance is already comfortable, native rendering can be attractive. If the GPU needs help, an appropriate quality upscaling mode can be a practical compromise.