appylover, for your first question, the difference is that the Myler combo bit has a gag action where the cradle bridle does not. The rings on the Myler one are set one below the other, like in the Wonder Bit, where on the cradle the small ring is actually set inside the big ring not creating a gag like effect.
For your second question, Parelli has 3 mouthpieces to choose from based on the horse's Horsenality, which is based on how much tongue contact the horse does or does not like. Some horses need tongue contact, which is what the C1 is for. Some horses need a little tongue relief, but not totally, which is the C2. Some horses hate tongue contact which is what the C3 is for, to give the horse ultimate tongue relief. By the time the horse and rider are ready for the cradle, it won't matter whether it's the C1, C2 or C3 mouthpiece because the horse is already prepared for contact.....the rider will just pick which mouthpiece best suits their horse's needs.
For your last question, the cradle wasn't designed to be a leverage device. When you attach the reins to the small ring you do get more 'lift' but it's not your typical leverage, if that makes sense.....when attached to the small ring the bit is activated less and a lot of horses actually like the small ring setting better, my horse being one of them.