Dedicated server for mobile multiplayer

When I build a dedicated server for communicate mobile clients, is necessary to leave online subsystem null?

Or I can plug for example googlesubsystem with my server to get acces to all stuff like a leaderboard, in-app purchase ect?

And if so, how can I use both of online subsystem for googleplay and appstore? Or its impossible and I have to use something like gamesparks or playfab to get all the stuff?

you can plug googleplayersubsystem with a dedicated server.

but the question is, do you know how to create a dedicated server and know how it works?