3rd party apps typically require BIS data plan and not any other type of data plan for another phone, I don't see why you would want another type of data plan on your account if your using a BB.
The native BB browser only works through BIS, unless you have the wifi browser that typically is installed as well but that only works when wifi is connected somewhere
GSync is OTA, you install the app and it syncs with you Google Account, GMail only connects through BIS I believe. But if your connected through wifi you can go to the www.gmail.com
and check your mail that way. Yes GMail works with labels if you turn them on as well