Get some regular soil with NO NUTES, promix HP works great stay away from Miracle Grow. Oh and most important KEEP IT SIMPLE. Your getting to anxious about little things, dont worry about anything till it actually happens. Soil will be way more forgiving, Always dilute nutes, especially in hydro systems, Remember to start low because you could grow with Only water so Even a little is a lot!
Root rot would only happen if your over watering and using soil that is compact and muddy. You want some nice airy soil, add some perlite if its not premixed. And biggest thing is to Not Over Water, I sometimes go a week without watering my bigger pots, Stick your finger in the soil, if its even a little moist its probably fine.
Its like this, when you transplant into soil your going to make sure not to pack down the soil around your plants, the first time you water the soil settles and the water quickly runs down and soaks the soil. If your smart and wait a few days to water you will notice that the top of the soil will be dry crumbly and chunky, and most important it will be quite lite and airy, so the next time you water, the water flows through the soil easily, then drys out the same way so you always have airy soil.
If you over water and your watering when the soil is already wet, then the water will pool up on top and start to get muddy and the soil will get too wet and too compact, and thats where the problems will start.
any plant with 4 nodes or around 6-8 inches should be planted into a Min 11 L pot, that will give the roots lots of room to stretch out and they will grow fast!!!
Your obviously only in Veg so I dont know what your feeding them, But I give all my plants just a basic full coverage veg hydro veg nutrient, I use GH grow and Thats it. Check PH and use good water and your good to go, dont over do the nutes for veg, Some Diamond nectar is also a good GH product.
Just remember not to overdo it, soil is so easy and forgiving, if you overdo the nutes you simple give them some plain water on the next watering and then resume your nutes with a more diluted solution.
Its basically Hydro bud grown in a Neutral soil / pete moss medium.
Anyways I hope this helps, just remember to keep it simple.
peace