One signal notification in ionic native

Hello guys,

I am stuck at this very basic question on implementing push notification in ionic cordova android app.

My very first question is for implementing open signal notification do i need to use both push and opensignal modules in ionic, or just any one of them?

and also if i am using open signal for my push notification purpose, do i really need a google projectid to implement it in android?

OpenSignal or OneSignal?