One thing I noticed after loading the kext is the following: when the login screen appears after power-up, after say a couple of seconds it's like if a layer is removed off the screen. The picture appears slightly less defined, but it still looks great and it's like it a layer of extra contrast has been removed. And this is before logging into any profile, hence I don't expect the screen settings of any specific profile to have an effect there at the start-up page.
Another thing I noticed after injecting the kext is that, when the Apple logo appears after power-up and the bar is loading, it would stop for a split second halfway through when I was on 10.15.2, and now that I am on 10.15.5 it gliches for a split second at the equivalent point.
On a side note, 10.15.5 looks slightly different from 10.15.2 to me, there is a bit more contrast everywhere I'd say. Other than that I have no issues, but then again I've always been fine with the iMac except that one month in summer 2018 and that single day this week. Sure, there is still way too much light everywhere on the screen and my old LG G2 is way more relaxing to read things on, but at the same time no more nausea, headache, dizziness, etc.
After using KextBeast, ahkinject.kext is present in two folders within my iMac::