If they have detachable hardpoints then you can potentially have a new combat tactic — at very long range fire PL-17 to target high value targets, ditch the hard points after the volley, and then close in using stealth mode and mop up what’s left.It will be cool in terms of capability to see long range AAM like PL-17 carried by J-20 in beast mode.
Even in beast mode, J-20 will likely be much more stealthy than J-16 and thus could get much closer to the enemy forces before launching its AAMs. The closer the AAMs are launched, the more likely enemy planes will fall into the no-escape-zone of the missile and thus become a guaranteed kill.