You can also put AOD off without lower power mode.
You have at least 50% more battery life.
Low power mode only puts AOD off and reduces CPU usage by reducing background activity (things that your Garmin is not doing like getting mails, refreshing app content, reduces LTE usage ...).
It doesn't reduce any workout feature, you still get the full precision from all sensors.
There is also un ultra low power mode which reduces GPS and other sensors sampling, but it's more extreme and should be used only for super long trails.
I am very surprised that an ex AWU owner like didn't know AOD was available on it