The “snaps, crackles and pops” in your neck are due to the irregular joint surfaces. When degeneration occurs to the facets, the normally glassy smooth joint surfaces develop ridges (peaks and valleys).
These ridges “catch” on each other and create the noises that you are so familiar with. Rarely, a ligament or capsule might catch and pop which could make a large sound.
Stretching can induce increased motion which in turn can cause more neck noise. If I use my imagination, the activator tool could under very unusual circumstances cause these noises but as I noted before, it is a very benign tool.