The regular GooglePlayGames plugin works , but only for web-applications. You CAN use it even for cordova (mobile) apps. But it will NOT use the googlePlay native app to login, it will send you to the web browser-> login Google account thingy.
It looks unproffesional and really really UGLY. (If you use this plugin for mobile apps, you set it up as an web app in google play console, NOT android app, since this plugin just uses the web interface)
You do not need to add any plugin in the compiler.
If you use the cocoon GooglePlay plugin, it works with the native android GooglePlayGames-sign in, which is smooth and really good. But this plugin really do not have any behaviours for requesting scores and show different players etc. It is just a "link" to open the Leaderboard in the native GooglePlay-app. This is ugly as hell, and is not a fine solution. Since you of course want to have the leaderbord within the game! (who designed this plugin? many features are missing)
The cranbery plug I have not tested, does it work with native GooglePlay sign in (like cocoon) AND does it have actions for requesting scores/data etc (like the regular Scirra GooglePlay plugin) ?
I know you have deep knowledge regarding this, am I correct on the above? AndreasR , Artpunk .