There is many arts/ways to choose, and maybe you should not think about the art itself. Because a good instructor is more important than the art. There is properly some people that disagree with me here.
The size of the person doesn’t matter, but the techniques that you are using is important depending on the size of the opponent.
Be smart when you decide what art you want to train.
Self-defense is under change every day. There is always smart brains that combine different styles and techniques. Some styles have certain stuff they need to learn, and other arts is combining many arts and searching all the time.
Nothing is bad, because you learn to handle the advantages for your style. Then you are trying to keep the opponent at this range.
It is really does not matter what system you are training, because if you are good then you can easy adopt techniques from other arts.
Therefore, you need to train head, body and techniques. But to be able to modify techniques or see solutions that can be used you need to have experience.
A good trainer does not need to be a good competition fighter, but he need to have a good understanding. So if you like your trainers and the way he/she train you, then you will learn much faster.
When you train Defense systems many people thinks that it is not a team sport, but my opinion is that you need sparring partners to get better. If you do not have that, the progress will be a lot slower. So you need to communicate with your partners.
Normally we talks about ranges and which techniques that can be used on different ranges. I like to define it as long, medium, short and close range. As closer you are as higher risk to get hit or locked, but it’s also better for you to hit or lock.
When you are closer you need to be aware of the centerline. I operate with two centerlines, mine and the opponent. Centerline is the center of your body, and your opponent. If the techniques ends there then it’s having the hardest power. This is also working in Locks and throwes.
So how can you get away from the centerline? It’s easy if you know how to do footwork, and move your upper body. But sometimes it can be too late, but then you can intercept, tap, trap or cheat the opponent.