Here’s where the trigger stops with the shim in the barrel hood on the Gen 5. The pencil mark on the trigger guard is the reset point.
Here is the same shim in the 19 and the reset point. The trigger stops a little farther out. Gen 5 mags seems to work fine in the Gen 2.
Magwell comparison. This pic also highlights how much thicker the trigger guard is on the Gen 5
Not sure what that rust coloured filth is in the slide. It kinda looks and acts like dry lube.