Just bench racing never seen a study.
Not putt putt, but 1000 below or up against the limiter to get good carburetion form those simple carbs.
Now, depends on the overall load, or if the engine is undersized.
Generally a Lower engine speed without lugging = less wear.
Remember 1200 rpm is ten power strokes per second in a 4 banger. That piston is moving and floated. So is the rod.