On iOS 8+ and Android L+, PhoneGap basically supports everything the system browser does (Safari on iOS and Chrome for Android, although on Android PhoneGap is locked to the version of Chrome that is built in to the OS).
The main problem with PhoneGap is some SDKs require opening new windows, e.g. for login prompts. In PhoneGap opening a window doesn't work because it's not a tabbed browser, it's just a single view making up the app. So I think the Facebook, Twitter and Google Play plugins don't work, simply because their login flows rely on opening windows, which does nothing. It should be possible to work around that, but it can be tricky - the best solution is if the SDK developers like Facebook are aware of this limitation and design their SDKs to work within PhoneGap.