they dont have to be 12in to flower, flower when you feel necissire, and i dont belive the size of the plant has to do with dense/fluffy buds i belive its ur lights an the genetics or you plantyour bud will still be the same quality as long as the buds have enough time to fully develope. Yes plant must be atleast 12 inches to start flowering. The diffrence is your yeild amount. Smaller plants mean less produce. The only diffrence other than crop yeild ive seen is small plants produce fluffy buds were bigger plants buds are denser making them heavyer.