In most cameras, the sensor captures at its native resolution. Lower JPEG resolution settings are usually created by downscaling that full-resolution capture in-camera. So comparing a low-resolution JPEG upscaled to match a high-resolution JPEG mostly compares scaling methods, not the camera’s true ability to capture more detail.

Because of that, your proposed test is not a reliable way to find the “minimum resolution that preserves maximum detail.” It can be influenced by the camera’s firmware scaling, your software’s scaling, sharpening, compression, and artifacts.

If you want a more objective comparison of image interpretability or usable detail, look into a standardized evaluation method such as NIIRS (National Imagery Interpretability Rating Scale). It is not perfect, but it provides a recognized framework for judging image quality.

So the key point is: different in-camera resolution settings usually do not change the sensor’s captured detail; they mainly change how the image is resized and stored.