Well, really the chances of having to wipe/reset a device after a pushed update are slim. That said...
games / apps themselves won't matter as they are all registered to your google account and should re-download regardless of what happens. However, your scores/levels on games wouldn't be recovered.
If your music is synced through google music that will all re-sync as well including your playlists. If you have music locally installed and run a 3rd party player you'd be out of luck on that.
You'd also lose things like your call log, text messages, and settings like ringtones etc.
I *think* that the stock google backup does save settings (ringtones, wifi passwords, bookmarks) but I am not sure what else. It would appear that 3rd party apps CAN make use of it, but that falls on the developer.
However, none of this helps answer the question of how to backup everything if you aren't rooted. And my answer is.... I am not aware of any one program that will. You may need to do it manually with multiple methods... and even then I don't have all the answers.
Google backup for apps and settings
manually copy music and playlists to your PC (if using 3rd party app)
app data like high scores / levels ????????
saving text messages / call logs ??????