Bursting Plague/Plague burst mechanics - Help needed and discussion

Bursting plague is a support gem that stores poison damage as plague up to 10% of the enemy's maximum health, and triggers an explosion on death. This explosion deals 100% of the stored plague as physical damage (in other words, 10% explody). I wanted to understand how this explosion works. The component of the support is called Plague burst, and has the AoE, physical, chaos and trigger tags.

I went into a map and messed around with supports. First, I linked my Poisonous concoction with bursting plague and wither, and noticed the on death plague burst explosions were applying wither. This lead me to think that support gems affecting the main skill also affect plague burst.

I also tried brutality, and it stops the wither stacks from happening (no chaos damage), and it does noticeably more damage. If so, this would mean that magnified effect is a great support if your main skill can benefit from it, since it will affect the AoE of the explosions, and it also means that Deadly poison is awful since it has a 25% less damage penalty on the hit damage, which could potentially be replaced with a different support for clear to boost the on death explosion's damage.

Thoughts on this? Anybody else has had any experiences running a different setup with bursting plague poison builds? Im open for advice. Playing a pconc pathfinder.