Thank you for the "welcomes" guys .
Thank you for the suggestions Sacred Plant Warrior.
I was thinking to add compost too because I say to myself: normally plants grow in dirt, so if I want to grow them in a more" like natural "manner possible (obviusly indoor is not natural but..) I can add it to the cocco so I can have the benefit of cocco but not impose to the plan a too much different medium from the natural one.. But, like you say, for the start, maybe better stick to a "classic" approach =).
About the pots; it's not something like : more roots space = bigger plant ?
About light: good point, so maybe I don't need a too much big pot see I don't want my plants grow too big