yet again not to compare with lets say a pixel 3 or samsung 9 or any OLED screen for the matter, but the brightness it achieves is more then perfect

For Max battery, drop the resolution down to 1080p and turn on adaptive brightness

More typical screen-on time is about 5.5 hours with 100% adaptive brightness and res to 1080p

Worst I've seen so far is around 4.5 hours of screen-on time at full brightness without adaptive brightness enabled, full RGB brightness on the back, while playing YouTube videos in split-screen with Facebook and Reddit, around 50% volume

You can leave the brightness to 100% if adaptive brightness is on, you won't notice really