My pics are of the C8. For SDR, which I assume will be the majority of your watching, I use Technicolor and my OLED light is at 55 or 60 and brightness is at 53 or 54. I'm a preference over reference guy. For movies, I use the Dolby Vision Cinema Home preset when applicable and the default Technicolor presets for HDR10. All are plenty bright enough.
LG 77C8, Sony 75x940E, LG 65B7, LG 65EF9500, LG 55E6, LG 55UB8200, 2 TCL 49S515's
2 Apple 4K TVs, 2 LG UP970's, 2 Samsung UBD-K8500s, WD 4TB NAS
Nvidia Shield, Wii U, Playstation 3