Install activity launcher from playstore.
inside activity launcher search and launch:
this will show the preinstalled themes. choose "colorfull international" for round icons.
this will allow to switch the quality of the screenrecorder from sd to full hd.
this will let you choose between all 8 color modes of the screen.
here you can enable 120hz for the screen. It will apply once you leave the menu. standard settings and the refreshrate notification won't show the new value.
you can see that 120hz is working by dimming your screen and toggling between 144hz and 120hz and entering recents screen eachtime you changed the value. The brightness of the grey Background in the menu will be different.
To use the standard refreshrate settings again you must enable "default auto Fps" in the hidden menu.
here you can see the actual fan speed. Yes its + - 15k rpm.
You can create shortcuts to these menus by longpressing on the desired Activity.
Tested on global 4.05 rom.
there are allot more hidden features like battery percentage in status bar, fingerprint calibration settings and battery stats. But they don't seem to work properly.