You can use even single tracker for all your hubs or links. Using different trackers help you to track the effectiveness of different trackers used for different links. To make things more clear, you assume that you posted 4 articles on different sites.
You used different trackers for each site. Now you can track which tracker resulted in more sign up and which tracker attracted more traffic to your hubs.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.