I am using straight lines connectors between tables with 90 degrees elbow points. I find that I am spending more time than I wanted to moving around connectors to have a nice and clean look, especially when there are lots of tables involved.
I noticed that when I move the tables around, the connectors are not placed using the shortest distance - if possible - they tend to retain their elbow points but that leads to convoluted links. I have to admit, it’s hard to explain without showing it. Check out the two images. Genre is below Film to start with, and the connector is straight. Then I moved Genre to the left of Film and the connector is below them. An optimal connection would have placed the connector between Genre-right to Film-left or Genre-bottom to Film-left. Using the Optimal style to All lines has disadvantages, especially if you have more than one link between two tables - sometimes they are overlapped or very close. The other thing that I want to avoid is selecting Optimal style every time I move a table. I want the tool to do it for me.