SDR and HDR (and the various types it supports) have their own preset. I can't remember my settings but once I'm happy with adjustment I have used the copy settings to each input feature to save replicating them. For HDR I reduce default settings to make it look like SDR and maybe + 20% higher output. If I leave everything at default (apart from disable NR, motion, AI etc) 100/100 for contrast and OLED it's just too bright, I don't know anyone could watch that- perhaps in a bright room, but in a dimmed or unlit room (bias light on mine) it's unbearable.
In Alien HDR, the landing sequence I compared to to my standard 1080p, the lights do appear with more contrast, and I suppose more accurate real life, but because I've reduced it, it's not so bad you have to look away due to the light output.
If new gen OLED are several factors higher light output, I can't see how people watch them (or LED as they are bright as well)
I would have thought TV's would do some self calibration, they take in ambient light levels then determine correct HDR values, there is
Contrast
OLED backlight
Peak Brightness
Dynamic Tone Mapping (in your source and TV as well)
Which all effect the light output