Sooo, been looking at quite a few videos and most recommend turning auto-brightness ON. But the thing is, does turning it on auto really helps saving the battery life in the long run ? How does this auto brightness system work ?

When I'm indoors, it brightens up more than I need so I have to dim it down manually, when I'm outdoor, it dims just fine, so not much of an issue there, but just want to ask do most of u leave it on auto or turn it off and adjust manually ? Which is the best in terms of battery management ?

if at all this feature does "save" battery life, it would be offset by your other activities on the phone.

to me, the auto-brightness (TrueTone) aims to provide the user with a better display and that is all there is to it.

Absolutely agree
But then, since day 1 I off the auto brightness and true tone, hence I will adjust manually
As I feel the screen feel warm, I didn't like it

so basically u keep it off all the time ? I did keep it off ever since i got the phone, but was thinking turning it on would save battery and would be better overall, but then having second thoughts.

As turn off all the time, if want to adjust brightness just adjust manually