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I'm still on Windows 10
You are right, I am very used to bright screens. When I lowered brightness to 42, I felt like I couldn't appreciate the details in the picture, even the Windows desktop looked bland and washed out. I will try to lower it at 60% and use it for a few days, see if my eyes adjusts to it.Initially 42 or lower will seem dim, because your eyes have been so used to bright screens, but after a few days anything more will feel too bright.
Ultimately brightness doesn't matter for colour accuracy or HDR anyway, in HDR mode the content controls the brightness and you are locked out anyway, this is purely for preference and the conditions you are in when using the display.