I'd stay with the 2 stage wedge design.
With easy to pop wood, about anything works. A steeper wedge pops the wood sooner, thus shorter stroke, faster cycle, and more production.
With tough stringy wood, (which is most of what we have here), the steep single angle wedge takes more force to operate and stalls easier. The splitter unloads to slow speed high pressure more often to finish the stroke. That means slower cycle and less production.
The theory of the two angle wedge is that the leading sharp angle cuts and separates the fibers like a knife. Then the wider second angle tries to pry the two wood halves apart, much like you pull apart two halves not quite separated at the far end, by grabbing the near ends with each hand and pulling sideways. The prying action of the second angle either causes the fibers to separate and the split to run ahead and ‘pop’, or at least puts the wood in separation and easier for the first sharp leading edge to cut. It would be similar to cutting rope or rubber or cardboard: pulling the two halves apart with tension makes it easier to cut.
A finer angle on the first wedge is easier to push in, like a sharp knife. The longer the distance back to the second steep angles, the longer the 'leverage' of the steep angles to pry the wood apart. So finer angles and longer wedge (to the second stage) is more efficient, but takes longer stroke to accomplish the split.
There is probably a different most efficient combination of angles and distances for every type of wood and grain and moisture. In real world, every day is different conditions and wood.
If you have mostly straight grained easy to split wood in your area, go wider on the angles faster. Single wedge might work just fine.
For tough nasty fibrous wood like elm, I would stay with the two stage wedge: shallower front angles and a second steep angled stage later.
Butch apparently knows that elm well. Pieces end up looking less like stove fuel and more like fur balls......
It would be interesting to build several types and try them on your local wood.
And not to be losing sleep about the ultimate, perfect, most efficient package, as ANY combination will be better and faster than a maul.
kcj