This can be quite confusing not only for beginners.
Why for so many properties to be properly disabled you have to check the Enabled checkbox and then un check the checkbox next to it?
Also in order for a light to cast ray traced shadows you need to un check ‘Cast Ray Traced Shadows’ on the light itself?
If your talking about Post Process settings, I’m pretty sure it’s done because they are meant to be blended. The checkbox then determines if the value on the current Post Process settings is valid, because otherwise, blending would be very annoying to configure.