Hi! To make a water only soil you need the minerals that the plant will need during the grow and you will need microbes during the grow to convert those raw minerals into a form that the plants can use. A water only soil is called a super soil, and is typically only used in the bottom third of a container, while a good base soil is used for the rest... so you don't need as much of it as you might think. If you can source them, several versions of supersoils are now being sold on the big box stores, but if you don't have access you will have to source the materials needed and will have to mix them yourself and then allow the soil mix to mature for 3 months or so before using it. Check out the popular soil recipes and see how many of the components you can get... and then we can talk about how to substitute for the rest.
Regarding the light... it will be enough to get you to the end... but it will be the limiting factor in your environment... I would suggest that twice that would be better, especially if you veg out your two plants for a bit to produce some large plants worthy of sitting in a 4x4 tent.
Regarding the light... it will be enough to get you to the end... but it will be the limiting factor in your environment... I would suggest that twice that would be better, especially if you veg out your two plants for a bit to produce some large plants worthy of sitting in a 4x4 tent.