To your first question, I don't get any slop when my Cannon rigger is screwed down tight. I use the same base that I believe you are using. My base is connected to a traxstech swivel base, which is seated to a track, so maybe that's why I don't get that slop. Not sure?
The noise you are hearing is normal. That's the positive ion control working. You'll notice it gets louder when the wind picks up. It can be annoying I know.
Mine aren't seated to a track and there is a little play. I have four mag 10's and I never noticed it until you mentioned yours. One had a loose knob today and I tightened it and there was no play. The rest were tight but still a little play. Probably just a normal thing.