Are Draco and Harry foils or parallels of each other?

You could make a convincing argument for both, but I believe they are parallels of each other. They are both very intelligent and charismatic kids, and even both end up playing Seeker on their respective Quidditch teams. They are also both the leader of a small band of three students that later expands to a large group of students.
What is more interesting, though, is how they both act as "Chosen Ones" to some extent. Draco is chosen by Voldemort to act out his plan to murder Dumbledore and is seen being mentored by Snape for that very purpose. Harry is obviously the chosen one to kill Voldemort and is mentored by Dumbledore himself to raise him up to do that.