Now design aside, if I display only one ad unti will I automatically get the highest paying clicks in that ad unit? So basically, do I want one well placed ad or multiple ads to increase click through rate (thats a big assumption I know)
One add doesn't usually affect another add. Sometimes they will come up with the same things. Usually, the highest paying first.
My advice is to try with only one ad unit and you will see how it works. You can change it anytime and add more units if you think that it is better.