Does the shape of connection lines in FME Workbench have an effect on the performance of the workspace? You bet!
ALL PROOF IS in this video.
With square corners, the data is slowed when it reaches the corner. It can become bunched up and affect the performance of each transformer it passes through.
Curved lines have a similar effect, although not as severe because their corners aren't as sharp. However, they are longer lines, and so the data takes more time to pass through.
Straight lines have the benefit of being the shortest line and having no corners. As you'll see in the video, they are by far the best way to speed up your workspaces.
It's not mentioned, but also be careful not to cross connections. Features can collide at the crossing, knocking off some of their vertices or attributes.