Does knowledge of the storyteller affect our understanding of the tale?Specifically in relation to the Pardoner's Tale compared to the Miller and the Prioress.
Our knowledge of the Pardoner certainly influences our understanding of "The Pardoner's Tale" in Chaucer's The Canterbury Tales. In fact, it is central to our understanding of the tale. One of the things that makes Chaucer stand out is his use of irony. Without irony "The Pardoner's Tale" is just another religious, didactic allegory.
The Pardoner is extremely greedy. He does what he does for money. He is corrupt. He is supposed to be doing God's work, but he only pretends to be serving God. This is itself ironical. But the irony is enhanced when he tells a tale that demonstrates that the root of all evil is greed. The Pardoner himself tells his audience that he uses this tale to separate listeners from their money. Thus, the greedy Pardoner tells a tale about greed in order to feed his own greed. There would be no irony without our knowledge of the Pardoner himself.
The second part of your question is confusing. I'm not sure how to compare a tale with two characters. I've taken care of the first part of your question, and I'll let another editor tackle the second.