Its not so much about plant height, its about amount of time to grow them through til harvest. A big plant will yield more, but it may take 4 months of growing to do that. a bunch of smaller plants that had no real vegging time to speak of may get you the same amount of bud, but in half the time at 2 months. Therefore your yield is better because you could conceivably grow twice as much in the same time.
You need to get a few grows with each breed of plant so you can get to know what it likes and doesn't like. how big to get the best overall results in the least amount of time, nutes to use etc etc etc.
Looks mostly Indica dominant, more than likely its a hybrid of the 2 types. Should be able to flower in 7-9 weeks with most indica dominant plants, some might take more by a week or 2.