See information here. Also some more posted here.
“We’ve also released Integer mode support for OSX. This disables some unnecessary processing steps within CoreAudio.”
> Integer Mode is an interesting one, only for OSX 10.9+ where they reintroduced the feature. It tells CoreAudio to do some processing without a (lossless) conversion between floating point and integers. Because this is lossless (for 16bit and 24bit), the bits going to the endpoint are identical. However, it gains some efficiency in the process, and thus could have an audible impact by reducing electrical noise created by your system.
Speaking for myself and as a Mac user, no reason not to enable it. Whether you will hear a difference with it on or off can best be determined by trying it. There is downside to using it from my point of view.