OS used to make an actual roots-blower type supercharger equiped 120 4-stroke. They apparently don't make it any more. It looked like a rather big box where the carb would be. When I say big, I mean it was about as tall as the cylinder, almost as thick, rather wide. It really increased the size of the engine.

In the small sizes of our engines, it would appear that the approach taken by YS produces more power for less weight increase than a full up blower arrangement. Other companies also use pump systems to shove more fuel and air in to the engine.

A ram air venturi really wouldn't be that effective by itself, but you can get more power from an engine by makeing some modifications that smooth out the airflow in and out of the engine. Putting a "stack" above the carb is one way. There are various tricks you can do to the crankshaft, ports, and other parts of the engine to get more power as well.

On two-strokes, you can install a tuned pipe. It pretty much does the same thing as a supercharger, though in a different way. But the end effect is more fuel/air mixture getting in to the engine and more power.