You could try the new option Resoultion Scaling, or use Blend Mode 0.0, at least for this game. With some settings, which tend to dissolve dithering, clear thin horizontal black outlines aren’t likely to get a good contrast, because the ntsc code blends it relentlessly with neighbor colors. 
With math terms, the answer is rather simple if we look at the matrix and compare it with sRGB. The red color component gets less weights (0.408979 vs.0.412391) if multiplied only with a red color, blue and green get a bit more.
If red gamut is a bit wider, the changed matrix tends to enhance the red color component with mixed colors though.
But it’s more of a question how much clipping and if you get the desired colors in general. I wouldn’t mind very limited clipping too much, since it doesn’t affect very saturated colors, or in a negligible manner. Best answer would be to reduce brightness in the pre-pass a bit if it’s notable.
Regarding this aspect the usage of a lut is more advanced, but with a lut generating program like DisplayCal you cannot miss the concept that color profile conversions are not this trivial and you get to pick a preferred conversion type.
