Very Low. Most APK-based methods rely on Linux kernel exploits. By version 7.1.1, Google had patched the majority of these "exploits," meaning these apps often fail or result in a "Strategy Not Available" error. Device Support:
Rooting will almost certainly void your manufacturer's warranty. Root Android 7.1.1 Apk
For a stable root on Android 7.1.1, the community-standard method involves: Unlocking the Bootloader The Importance of Rooting Android 7