Is the experience of bhanga (5th insight - knowledge of dissolution) the equivalent of the destruction of the khandhas?
No, in the knowledge of dissolution the khandas are still there. The Visuddhimagga describes knowledge of dissolution as follows:
Visuddhimagga XXI (10-11)
When he repeatedly observes in this way, and examines and investigates material and immaterial states, [to see] that they are impermanent, painful, and not-self, then if his knowledge works keenly, formations quickly become apparent. Once his knowledge works keenly and formations quickly become apparent, he no longer extends his mindfulness to their arising or presence or occurrence or sign, but brings it to bear only on their cessation as destruction, fall and breakup.
When insight knowledge has arisen in him in this way so that he sees how the field of formations, having arisen thus, ceases thus, it is called contemplation of dissolution at that stage, 7 with reference to which it is said: “Understanding of contemplation of dissolution, after reflecting on an object— how is this knowledge of insight? “Consciousness with materiality as its object arises and dissolves. Having reflected on that object, he contemplates the dissolution of that consciousness.
In other words, it is called knowledge of dissolution because the mind is focused on seeing the formations break up and cease.
When you reach Bhanga you still have ego. Ego is mainly due to Sanna. To dissolve this you have to look at
contact > sensation > perception > through proliferation > sensations process and try to stop the thought proliferation / conditioned response of you mind / identification and perception about the world.
With Bhanga you can quickly rid any formation by brining you attention to the sensations associated with Sankhara.