"120 luminance, 5600°K white point, 1.8 gamma"
Why would you use a Gamma 1.8? There was a Mac based myth over twenty years ago that Macs were supposed to be Gamma 1.8 but that was just a myth and it only because Gamma 1.8 sort of matched up to the very early laser printers.
It's much better to keep your monitor calibrated closer to it's native gamma, which is usually 2.2-2.4. The advantages of that is that there will be less correction in the video card lookup tables which would force a simulated 1.8 resulting in even fewer actual viewable levels on screen. This would not be as big an issue with an Eizo that does internal 12 bit hardware calibrations before sending data to the video card, but very definitely an issue with an iMac that starts at 8 bit and goes down from there with any video card LUT correction.
It wasn't a myth. Using 1.8 gamma was deemed correct and the system was designed for it, back in the days of CRT based displays. The problem was that the gamuts of CRTs at that time was not as well-standardized as it later became with the sRGB spec and Apple found that there were issues with gamut if they set the CRT closer to a "native" gamma (near 2.2). Setting the display to 1.8 gamma allowed them to split the difference between the controller board and the display with a more linear control capability while achieving a wide enough gamut for web-press printing (the basis of the Adobe RGB (1998) calibration spec) and for the early Color LaserWriter as well.
Modern LED flat panel displays have a native gamma in the 2.2-2.4 range and a native white point much bluer (6200-6800°K). Most modern inkjet printers seem almost totally agnostic to whatever gamut and colormetric you push to them ... the printer and inks have more range than the papers do. I tried the native specs when I first started using flat panel displays in the early '00s but I find those specs awfully contrasty and hard on my eyes, and I had to do more extensive adjustments to achieve the neutral outputs with the tonal curve I want for printing and exhibition display. After several rounds of experimenting, I determined that dropping back to 1.8 gamma and the much warmer 5600°K white point produced good results that I liked with much less adjustment required in the rendering. So that's what I standardized on in 2004 and have used ever since.
I've calibrated displays on at least three dozen iMacs (at least those past the ones with the overly-bright displays in the 2008-2009 time period) to these targets and had nothing but excellent results with them.
I worked for Apple for 24+ years, had access to both any machines I wanted and to all of Apple's hardware and software engineering folks as well. Most of my experimentation was guided and vetted by the people who designed the hardware AND software, and participated in the development of the ISO specs for many of these colormetrics ... I'm completely satisfied that I'm doing the right thing because I'm very happy with the results I get...
G
"In theory, there is no difference between theory and practice. But, in practice, there is."