JoJoe, the sand is to help with drainage and the larger the grain the better. I, sometimes, look in Aquarium stores for larger grain sand and some nurseries have bigger sand. Not sure about vermiculite but it is supposed to help with aeration but drainage is more the issue with succulents. Other small rock would also do about the same as sand but I think bag of small rock is more expensive. This is why when I dismantle a container of plants with rock dressing, I always save the rock dressing 'cause you never know when you might have use for it.
Not sure if you mean pumice or perlite.Both are volcanic rock. Pumice is what is found in our everyday scrubbing stones for dry skin. Perlite is used in planting mix to lighten the mix and help with drainage. Only drawback to perlite is that it floats to the top when container is watered and you get it all concentrated and white at top of container.
Don't know whether your plantlets will grow "faster" but given the right conditions they can grow healthy. I wouldn't expose plantlets to full sun exposure until they get bigger, but partial sun in mornng is a good start till they get more established in the right well draining soil. Wasn't sure whether your plants are inside or out but better to keep inside if your climate is cold now. In the future, definitely good light is important to keeping your echeverias (was it?) compact and in good aesthetic form and health.
