When making a sponge cake how does the method of combining ingredients effect the final product?
Generally speaking, a sponge cake recipe needs to create and trap a bubble structure in a mixture of protein, sugar, and starch. Since there are a number of ways to do this, there are a number of common techniques used for accomplishing that goal. The techniques are different and interactions between ingredients can be more complicated than they seem, so the effect of each ingredient might be different with each technique. Describing the ways that each ingredient interacts with each other ingredient in a cake is far beyond the scope of an answer on this site.

Almost every cake recipe that you commonly see on the internet is based on an older, tried-and-true technique from the canon of an older culinary tradition. On a blog or in a cook book, you might see a recipe for Aunt Edna's Famous Chocolate-Fanatic Fudge Filled Cake, but in the more technical terms that a pastry chef would use, it could be a layered chocolate genoise with a Godiva liqueur soaking liquid and ganache filling. Rather than checking out individual recipes, I'd recommend researching the broader techniques they're based on to get a better understanding of the mechanics. 

In my French/American oriented in culinary school, I remember learning about Genoise, Separated Sponge, Chiffon, and Angel Food techniques, which are all common in the modern western canon. There may have been more— it's been a decade since I graduated and I was never a pastry chef— but if you study those, you should get a pretty good idea of how cakes work in general.

As an aside, when you're testing/workshopping a recipe, like with any other kind of experiment, you should reduce the number of confounding variables. Use one recipe (or ideally, basic unadorned technique) and change the ratio of ingredients by increasing/reducing the amount of one ingredient at a time. This will give you MUCH better data.

A general question gets a general answer, but I think it will give you a good start. ;-)