For colors that fall outside the triangle, do we project them on to the nearest edge or does it not make sense to take about colors outside a triangle because the system is capable of representing colors only within the triangle and we can't really command the system to represent a color outside the triangle?

Also is there any reason why for example the sRGB color space is so restrictive? It seems like you can represent only a very small fraction of colors using it. Wouldn't it make sense to have as big a triangle as possible? And if our eyes are most sensitive to green, why is the greenish part of the sRGB triangle much smaller than the reddish or bluish parts? Wouldn't our eye pick up slight differences in green vs slight differences in red or blue