AK-48 and Master Kush. You won't be disappointed.

Both are relatively easy to grow, are known for their high yields and potency, and they finish quickly (50 - 60 days). Concerning height, you simply need to know what you are growing and then time veg growth accordingly. Assuming you have 4' I'm giving 1' for the light. That leaves 3' for everything else. You would not want to veg these much past 8 inches. That said, there are others here with far more experience so once you have settle on the strains you should post a question detailing your grow environment and seeking advice on veg height. Also, consider doing a scrog grow. See: An Overview of Cannabis Training (ScrOG, SoG, FIM, Supercrop, LST, etc.) Check my signature for some tutorials that you may find useful.

Note that I just purchased some nirvana seeds via seedboutique.com. They aggregate from a number of seed suppliers so you are not limited to one. Two thumbs up for seedboutique.