Another thing you can do is make sure every place the PEX or fittings touch the floor, a wall or pass through a wall or the floor that they don't touch. Add a piece of pipe insulation about 2 to 3 inches long at each spot. That will stop any pulsation of the PEX and fittings being transferred into the wall or floor as vibration.
I had a spot where PEX went through a hole at the bottom of the bathroom wall between the sink cabinet and under the bottom bunk. It touched as it passed through the hole.
I left a sponge mop leaning against that wall and the vibration between the wall and mop handle was very loud. Stuffed some padding in the hole and no more vibration.