Out-of-the-box battery life is much better on GrapheneOS. With a similar setup with 1 profile with sandboxed Google Play and the same apps, it will be slightly better on GrapheneOS due to having fewer apps than the massive amount of stuff present in the stock OS.
It's easy to set things up far less efficiently on GrapheneOS. As an example, Signal's WebSocket push fallback when Firebase Cloud Messaging is unavailable via Play services is quite inefficient. There's the Molly fork of Signal with support for UnifiedPush which has efficient alternatives to FCM, but since Signal's server doesn't support it this requires a MollySocket server to convert to UnifiedPush. There's at least one public provider. If you simply use FCM as you do on the stock OS then you wouldn't have any extra battery drain from running multiple often less efficient push implementations. It's common to want to avoid FCM to the extent possible, so people often do set things up less efficiently, but it's not because of GrapheneOS.
> Also, does this let you setup very restricted accounts like something for my parents so they can't go installing malware from the play store? (Parental controls are week in play store and malware rated for everyone in "weather" apps and the like)
You can use user profiles for this as you can on standard Android. If you want parental control software for those profiles, that's something you need to install. It's supported, but GrapheneOS is not going to specifically provide parental control and monitoring features rather than only the standard device/profile management APIs usable for it.
It's easy to set things up far less efficiently on GrapheneOS. As an example, Signal's WebSocket push fallback when Firebase Cloud Messaging is unavailable via Play services is quite inefficient. There's the Molly fork of Signal with support for UnifiedPush which has efficient alternatives to FCM, but since Signal's server doesn't support it this requires a MollySocket server to convert to UnifiedPush. There's at least one public provider. If you simply use FCM as you do on the stock OS then you wouldn't have any extra battery drain from running multiple often less efficient push implementations. It's common to want to avoid FCM to the extent possible, so people often do set things up less efficiently, but it's not because of GrapheneOS.
> Also, does this let you setup very restricted accounts like something for my parents so they can't go installing malware from the play store? (Parental controls are week in play store and malware rated for everyone in "weather" apps and the like)
You can use user profiles for this as you can on standard Android. If you want parental control software for those profiles, that's something you need to install. It's supported, but GrapheneOS is not going to specifically provide parental control and monitoring features rather than only the standard device/profile management APIs usable for it.