What you describe is most likely not two different rangefinder types, but two parts of the same kind of optical rangefinder/viewfinder.

On cameras like the Leica M9, focusing is done with a superimposed rangefinder patch, usually in the center of the finder. You focus by aligning the doubled image until it becomes one.

The rest of the viewfinder may show bright-line frame lines, which indicate the lens’s approximate field of view. Those frame lines are for composition, not focusing.

So the M9 and the Voigtländer you tried were probably using the same basic focusing method: a central superimposed-image rangefinder patch. The apparent “double image across the whole finder” was likely just how that particular finder looked to you, or how its framing/viewfinder presentation differed.

In practice, the useful distinction is:

• center patch: used to focus
• surrounding finder / bright lines: used to compose

That means you typically focus on the subject using the center patch, then compose using the frame lines if needed.