The official announcement was mentioned in Matrix’s blog post:
Next release 0.4.2 should also be published on F-Droid with push support using UnifiedPush.
In other news, thanks to Joshua, NeoChat now supports push notifications based on UnifiedPush.
Interestingly, the Element X issue regarding implementing UnifiedPush, has not been updated, and there is no related merge request that I can find. NeoChat appears to have their changes buried in merge requests.
Yes, the optimization is setting up how often the app and phone should wake up and check with your matrix server if there’s any new messages.