This is pretty important to understand if you want to play with water chemistry.
None of the common salts change the pH much in and of them selves, most in solution have a pH close to 7 (not Carbonates/BiCarbonates...).
How they change the pH is by Ca reacting with Phosphates from the malt, this forms insoluble Calcium Phosphates and leave H Ions in solution. pH is the count of the number of H ions in solution.
Calcium from any source reacts with and reduces the pH by the same mechanism. Clearly the limiting factor is the amount of Phosphate available. Some is freely soluble, some bound up in organic complexes, the free stuff reacts quickly and lowers the pH to mashing range, some becomes available during the mash, boil and ferment which is in part why the pH falls at every stage of the brewing process.
But (time) once you have used up all the available Phosphates adding more salts wont help you much.
Acids are different in that they just add H ions. Lowers the pH
Bases (Alkaline) like Carbonates mop up H ions less of them and the pH will rise. Which is why its pretty crazy to be adding carbonates to anything other than very dark beers. Dark beers get some of their acidity from Melanoidins and other Maillard products and can be too acidic (under the recommended mashing range)
If you add 100ppm of Ca in the form of Chloride, Sulphate or Lactate its the 100ppm of Ca that will affect the pH and if they are all fully dissolved to pretty much the same amount. Where it changes and what I like about Lactate is that both Cl and SO4 have pretty emphatic effects on flavour, Lactate doesn't so we can add the ideal amount of either/both Cl and SO4 then bring the Ca to target without screwing with the flavour we want.
Where it gets much more complex is when we start to look at buffers, if your interested Kai at Braukaiser
treats the subject very well, well worth a read.
Buffers resist change in pH, a well designed buffer complex will basically superglue your pH right where you put it and it wont move much at all. Lactate/Lactic Acid falls into this class - very handy.