Question about transfigured Chaos DoTs

If I am spraying Blight of Contagion (stack limit of 5) and my friend is spraying Blight (stack limit of 25) at the same boss, how many debuff stacks can be achieved simultaneously, 5, 20, or 25?

Are Contagion and Contagion of Transference different debuffs, such that a monster can be affected by both at the same time?