ok well ill give it a shot, "stiffer/more responsive ski boot" has to do with the forward flex and how hard it actually is to flex forward. 100 + is for the most part a stiffer boot and anything less than that is somewhat soft, but everyone will have their own opinion on this. This stiffer the boot, the easier it will be to transfer energy to your ski. the softer the boot the more work it will be to get your ski to do what you want it to do, thats a big reason why racers have super stiff boots, so they can get the most energy transmition to the ski with minimal effort compared to a soft boot.
As for skis, a softer ski vs. a stiffer ski will be totally a preference thing. A stiffer ski will hold up better at high speeds and be better for bigger jumps, but harder for the most part to butter. i prefer a softer ski for rails and jibs etc, more fun and playful.
Rocker skis mean that there is a reverse camber at either the tip or tail or both, basically they bend up when you are skiing so when you get in softer snow it floats easier because your ski is already angled up.
hope this helps!