A softbrick usually renders the user unable to boot into Android OS successfully and satisfactorily, and most of the time you can boot into a custom Recovery (you would be having it if you mentioned Xposed) and then use the ADB commands to restore the backup from there.
ADB backup method isn't useful in case of Xposed Framework since ADB doesn't make any image of
/data (Xposed makes changes into
/system). ADB backup is concerned with user data (Apps, app data, settings, and similar things, internal/external SD card data) only. That's why Nandroid is recommended and always preferred.
Note that the command you mentioned will backup only shared storage (SD card), all apps (user+system) data and their apks as well. That's just it, but not enough to run a system.