You may or may not do WCs during cycle. If you feel like doing so, do it. Not to hasten the cycle but to make the water more favorable for the already existent life forms in your tank, like worms or pods and other beneficial hitchhikers.
Silicate is from the sand, and a bit comes from the rocks. Decaying diatoms will leach a bit of it back into the water column as well. Phosphates and nitrogen in the form of ammonia/ammonium, nitrite and nitrate come from dead stuff. Like dead microfauna and decaying algae and uneaten food. It's very very normal to have diatoms and other algae during the first months of your tank as they are just utilizing whatever nutrients are present in the tank.
You can actually minimize silicates by doing WCs if you can manage to siphon the diatoms, since a large percent of silicates are already bound in the diatoms.
Another tip for starting hobbyists, especially those who would read this: Nutrients especially nitrogen (see above forms) silicates and phosphates are just some of the few things to test for during cycling. The main reason why most experienced reefers tell beginners to wait it out is because there are other things to look out for during the first few weeks of your tank.
When you use liverocks (cured or uncured or whatever term they use nowadays), living organisms in the rocks die.
They leach back the nutrients bound inside them, and bacteria (and algae if light is present) bloom. Making the water parameters fluctuate, pH typically drops because of too much co2, oxygen drops because bacteria use it to assimilate the nutrients in the water, alkalinity drops as well and other nasty crap like antibiotics from dead sponges, toxins from dead algae and other secondary metabolites released by dead hitchhikers fill the water column. These, my friends are the most important reason why we wait for our tank to stabilize. It is not just the nitrogen and phosphorous cycle. There is more to the tank than just the parameters we usually test for.
Haba no? So the bottomline is waiting is good and water change is good. Trust me, you can never make a living tank sterile (or overclean it), but you can easily pollute it
PS
Snails and other CUCs are fine but don't overdo it. They definitely are low contributors in the overall bioload, but only when they are alive. If you have experienced smelling a dead snail you'll know what I mean.