Yeah I'm also still learning ever more. I only know how to grow and multiply plants but all the theoretical bits like vpd, hormones and such I'm still learning. The most important bits to know are simple really. If you want to grow roots you need carbohydrates, which are created in the leaves. To support more leaves you need more roots. The roots only take up water and nutrients in their tips so you want them so subdivide often. The best length to cut the taproot off at is 4 inches; then it grows the densest amount of new roots from the tapwhich will be the big secondaries. Roots can't merge when growing close together so the bigger one will eventually strangle the smaller.
That's the reason cloth pots work so well. You kill the tip(air prune it) and it produces side shoots. Unfortunately Cloth pots have some disadvantages too; That's why I'm going to grow in the air pruning pots the Somangos are in from now on. I have however noticed that they took a longer time than I had liked to get to a subDivision level of 4/5 so the next time around I'm going to start my plants in half Liter net pots. Those will then be transplanted into their new 11 Liter plastic air pruning pots WITH the net pots. That should eliminate any transplant shock and ensure a higher density at a faster rate.
tldr: Roots are the important bit.