Resolution really only has to do with the number of megapixels accessed by the camera's operating system. The size of the sensor plays a key role in the quantity and quality of the light captured. A full-frame sensor with 24 megapixels will have a noticeably enhanced image compared to that of an APS-C or m4/3 sensor, as each pixel on the full-frame sensor is capable of capturing more information from the scene due to a larger surface area. Likewise, a 16 megapixel APS-C sensor will have larger pixels than a same-sized sensor with 24 megapixels, allowing for the capture of more light at each pixel location, allowing for a potentially greater dynamic range - at the expense of fine detail (resolution). Various hardware improvements, such as backside illumination (BSI), have helped to offset the loss of pixel surface area regarding low-light performance in some cameras, and the ever increasing onslaught of software solutions have helped to reduce or eliminate the advantages of the lower resolution sensors in low-light settings. I can't say that my X-T2 suffers in comparison with my X-E2S regarding light performance, and the resolution is decidedly better with the 24 megapixels of the X-T2 compared to the 16 of the X-E2S. The sensor processing engine in the case of the X100S vs. the X100F (EXR II vs. X-Processor Pro, respectively) will more than compensate for the pixel size difference, I'm thinking.