That Cedar Creek site was incredible useful for me in my first foray into electric brewing, which was building a heatstick to augment my stovetop mashing and turkey fryer boiling processes.
But keep in mind that the entire first half of the statement pasted above is a joke, not just the sentence before the parentheses. There are no plasma streams, these are simple resistors, not jet engines, neon signs, or stars.
The design of my kettle lead me to (somewhat arbitrarily) position my two 1500 watt elements about 90 degrees from each other, opposite the dip tube. I'm sure most arrangements will work well. I'd focus mostly on how you want the outside of the kettle to work for you, where you want wires running, where you want your valves to be, your comfort and ease of use.
You will have some people tell you about having your heat source slightly off-center (typically referring to more traditional heat sources) to help "turnover" of the wort or something. I suppose my way accomplishes that, but again I'm really not sure that matters too much.
Enjoy the new build.