I have unclipped with SPDs with them really cranked down to maximum tension..yes I have a 3mm allen key. They have a greater tendency to unclip when wet. In fact I think I have only had accidental unclips when riding in the rain. I have only tried the silver cleats and can't say whether or not the black cleats will prevent unclipping.
Crank brothers pedals are not adjustable, but they are designed to tighten as you pull up on them, and there is no way to vertically pull out without literally ripping the cleat out of your shoe. I've never pulled out unintentionally with an eggbeater.