BJJ most certainly requires strength. The point where you can beat a stronger person of similar skill based on technique is very far down the road, after years of training. Most people can't overpower a stronger adversary even when they have solid technique, as you're still reliant on the timing it takes to exploit your opponent and use said technique. In an actual fight, that window is probably in the hundreths-of-a-second category, and a big old dude can simply bend your arm into your face and lay on you if you miss your openings.
Krav Maga focuses on a lot of aggressive attack response, combining a defense with an immediate series of attacks that will hopefully incapacitate someone long enough for you to run away. It was created and tested in WW2-era Bratislava where it enjoyed many real-world applications, and is used by the IDF as well as the Mossad, who are some bad mothers.
Ground fighting and wrestling are great to know, but I wouldn't say they were the end-all of hand-to-hand fights.
That kind of depends on your point of view, or what you look for in a system- if that's practicality and ease-of-learning, or the effectiveness of the system as a whole, after you've learned and can actually apply it.
