Does ADB Back Up contain system files? Supposing an un-rooted android device has got an ADB back up and something goes wrong and the device does not boot up, then can the ADB back up be useful?
As for the second part of your question, you might wish to see Is there a way to look inside and modify an adb backup created file? Yes, it's possible extracting parts of it, and yes, Titanium Backup is one of the apps capable of this. Other ways are described in the linked question.
Also worth a look:
- How do you extract an App's data from a full backup made through “adb backup”?
- Partial adb restore
- Backup and restore Android Settings and Application through ADB
Answer taken from What all does ADB backup and how do I restore part of it?