Congrats on the transplant and overcoming your crippling anxiety about getting that done!
I don't believe that you
need large pots for LOS, you just need shorter grows if you go with smaller pots. The soil gets depleted of the nutrients that got cooked in as the plant grows, so if you wanted to do a short veg and flip, smaller than 7 gallons can work.
I think you are misunderstanding the word "microbe." Wikipedia defines it thusly: "A microorganism, or microbe, is a
microscopic organism."
How good are your eyes these days?