If your device is running anything older than Android 7.1, skip this section as your device will not be using A/B nor system-as-root. First, you need to know whether your device is using A/B partitions. If you don’t know, use a terminal (adb shell or any terminal emulator) to check with this command:

getprop ro.build.ab_update

If the result is true, then your device is using A/B partitions.

If your device is A/B, then your device is also certainly using system-as-root. To find out whether you are using system-as-root on a non-A/B device, use a terminal to check with this command:

getprop ro.build.system_root_image

If the result is true, then your device is using system-as-root.

getprop ro.boot.bootdevice