AngWay Ok so my open source apps will work on unified push?
Some might, but they have to be designed to do that. It is by no means common. Some apps also just wake up periodically to check (low-frequency polling, basically), without relying on any other service.
AngWay now is the protonmail app opensource?
Yes. But it does not support Unified Push. Requires Play Services, or no notifications.
AngWay "Sunup" and "NextPush" which one of these should i install and will it replace what google play services does with sending me my notifications?
They do the same thing (I think). More a question of who you trust. But they are not just a drop-in replacement for Play Services.
The vast majority of apps do not support Unified Push.