Fireeyeeian wondering what kind of battery life I could maybe expect
Compared to S20 and their Android version I have double battery life or something like that. Others report around the same. Some are trying to track down exactly why this is the case with some hints so far. To me it looks like too much bullshit is happening in the background in Samsung's and Google's Android versions.
Rooting GrapheneOS will only get you in trouble on all fronts. Just don't do it.
Can switch between swiping gestures and 3-button in the settings.
Close to all apps work on GOS. If something doesn't it might be just a question of wrong settings or wrong installation method (app store dependencies).
Recommend you read https://grapheneos.org/ since it's actually useful info for new users. Forum search will fill in more blanks.