One is an aluminum replacement blade that used to be sold as the GTX, and the other two are inserts that fit inside the stock blade.
All work on exactly the same basic principle: they add an adjustable point of contact between blade and sear lever that changes the basic geometry of the trigger to a true 2-stage type. Any differences (e.g., pull weight) result from details in the dimensions and geometry of the screw (e.g., fineness of thread pitch, angle of contact, and rigidity of support from steel-on-steel, steel-on-aluminum, or steel-on-plastic) that provides the 2nd stage contact.
Here's a post of mine, comparing the performance of the aluminum blade to the MicroGTX sold by Skyler McConahy.
And by the way, please don't refer to the current vendor of the aluminum blade by name. The owner of the forum doesn't think he deserves the free exposure, as he explains here: