1. To my knowledge all Cherry MX keys are the same size to make it easy to put in aftermarket key caps.
There are two types of plastic used in keycaps. Typically keybaords use ABS plastic since its cheaper, which has that smooth feeling and can tend to get glossy quite quickly with use. PBT is the other kind and has a rougher texture and doesn't develop a gloss so easily. I think Ducky offer aftermarket PBT keycap sets, though I'm not too sure.
3. Hence the advantage of mechanical keyboards, you dont need to bottom out register the keystroke. Lightly push down a key until you encounter resistance. That's the Actuation point, where the keystroke registers. Being Blue switches, when you push past that it should click. Any further distance you push the key down doesnt matter.
Particularly good typists can get a feel for just pushing past the Actuation and not bottoming out, but I know I cant.