Hi Wee,
While this is probably not the best site for legal cultivation of medical marijuana, I can offer some advice on your specific question.
NFT systems are generally great setups for growing leafy greens and light feeders. Primarily shorter term crops. I'm not sure if you are growing indoors or out, but the root system of the cannabis plant will most likely clog / back up the
nutrient film. The 2 liter flood and drain is a very good system built on a pvc manifold.
I've run12 2 liter bottle systems back in the college daze, and they work wonderfully under a 400w. MH/
hps. With what I have learned over the last couple of years growing food hydroponically for myself, I would suggest you also consider a return
drip system. But either will work well.
Your location and grow location would help (indoor or out). I see you are referring to metric measurements, I assume you are not in the states. Where I live the drip 5 gallon "Sack" systems are very popular for growing medical herbs, though I am a Bato Bucket guy for my veggie garden. Check out crop king.com for some more ideas.
Todd