I believe that your buds will put on the most weight during the final week or two before harvest. When the pistils start to turn brown or darker color and begin to shrivel up. Also the THC is most potent when the trichromes turn a milky/white color. You will need atleast a 30x zoom microscope to check them out for the best harvest time.

Indicas tend to be a shorter plant with wide fan leaves. The buds on indica are usually more dense with couch-lock stone. Sativa plants are usually tall with thin fan leaves. The buds on sativa are more airy and have a more energetic head high.