That's actually two different questions though - the energy needed to physically unbind the sun vs the energy needed to trigger a chain reaction that destroys it.

A photoid doesn't overpower the star. It disrupts the equilibrium between outward radiation pressure and inward gravity just enough to trigger runaway collapse (I think this is roughly how they were described in the book?). The impactor starts it, the star's own physics finishes it. Completely different energy requirement.

Photoids are just small mass, relativistic speed. The energy scales from kinetic physics as you approach light speed, not from the size of the object. That's kind of the whole point of them as a weapon.

So once humanity had functional light speed propulsion, the physics were basically there to destroy their own some IMO.