Does anyone know what the functional difference in between the various Romanian semi auto trigger groups is?

The best I can tell is there are 3 different shapes with regard to where the hammer interfaces with the trigger. One of them looks to be almost the same as the full auto triggers, butthe other 2 seem to hold the hammer at a different height, as well as having a shorter “shelf” and are generally taller.

I have pictures of the 3 different types here: https://www.flickr.com/photos/169215408@N08/?

Does anyone know what the functional difference is between these, and is 1 better than the other?