Hi Lisa, I don't know if I'm answering what you asked, but I can give you some thoughts from my experiences.
Last year was my first year of buying and using Perlite. I bought a huge bag of chunky Perlite 3.5 Cubic Feet. I read countless posts about not breathing in the dust, so I waited until there was a windy day and mixed the pro mix with Perlite outside. I didn't notice much lingering dust at all. I did not wash the perlite. I don't know if mixing it outside is possible for you?
I did look up 'Growit', but only found Apps at first. Then I added "hydro" to the search, and came up with
https://www.google.com/search?ei=9YX...13.bgboDbaA4y8 It's something I am unfamiliar with. I wish I could help.
The clay shards in the soil; again from my experience - the short version is that clay holds in moisture much better than silt, sand, and mixes. That can be a good thing if you don't get too much rain/overwater. Clay also holds more nutrients
https://homeguides.sfgate.com/soil-c...and-99972.html
A good mix of 40-40-20 mix in the above link sounds perfect, but I have a whole lot of questions.