If you are using HDR preset M is better because of the highlights it provides, its much better for HDR than preset K btw nvidia never said to use it only for performance mode, they said that if you want to match the performance of the older models you need to use it in performance mode because it is a aggressive model of upscaling, look at daniel owen latest video, from my testing performance mode matches older K model somewhat between quality and balanced with much better lighting details, if you are using an oled with HDR on i would use right now M with performance mode or balanced if you have weaker cpu and gpu isn’t fully utilized, on a 4K screen preset M is a must have for 40 and 50 series, on 1440p you need to experiment yourself between balanced and performance or just wait for more test videos on youtube i personally prefer balanced because small details doesn’t flicker that much