Various Martial Arts - Questions?
The key to an effective martial art is "whole body unity" for each and every movement and technique being applied. The body must be relaxed but still connected, with natural alignment of the body, the use of leverage and physics all play an important part in whatever martial art system you choose. Finding a teacher who understands how to incorporate all of the above into their martial art style is not an easy task, and therein lies the problem.
1. Unfortunately, the small guy mastering skills to defeat the strong and founding a style is very common theme in martial arts in general. Just about every major style has an example of it. For example, BJJ was founded by a member of Gracie family because he wasn't strong and wasn't able to compete against the strong judokas in his judo school. So he focused on the ground fighting that allowed him to dominate even bigger opponents, and progression of this focus lead him to develop Gracie Jiujitsu that became the foundation for BJJ as a style. Wing chun was founded by a small woman to defend her self against a tyrant governor. Sun Lu Tang was a small man that had mastered three internal martial arts and was able to beat multiple challengers bigger and stronger, and he goes to found Sun style Taichi. etc. and etc. 2. All styles work off of basic frame work, which is the human body. There are limited ways of using human body effectively to hurt other humans with an empty hand. That means there are a lot of overlap in techniques and methods, which is why sometimes it's hard to tell one style apart from another for a layman. The biggest difference will often be what is the general goal that the style is looking to achieve, what methods are they using to achieve that goal, and what is the practice method the style uses to get there. For example, kickboxing and karate would focus on mainly striking, and thus share many techniques in sparring. However the practice method is often very different with karate using forms and drills, where as kickboxing work combinations on heavy bag, hit mitts, and work on shadow boxing. The goal is often different as well as kick boxers often looks to train for kick boxing match as a main goal(even if you aren't looking to enter a match the class is structured around what would be effective in a match), and karate's goal is often in preserving tradition as much as trying to make the art effective for general self defense. I'll quickly list a very general description of each art, but it doesn't apply to all schools, instructors, and practitioners and I would actually advise just youtubing the styles to just get better idea on what they are like. Kung Fu - It's a general word used to describe any martial art that has its origins in China. Essentially Kung fu = Chinese martial art. It's kind of like saying Japanese martial art, to which a person would respond with 'which one? Judo? Karate? Aikido? Kendo? Etc.' If you read a sign that says kung fu, you would have to walk in or google which exact style the place teaches. Personally I like Xing Yi Quan and would recommend checking them out, but as a general example of kung fu I guess long fist, wing chun, and taichi would be the ones to check out. Tae Kwon Do - The origin of the style is a bit controversial, so I won't go much into it. It's essentially a Korean martial art that has traditional practices like forms and such, and focuses a lot on kicking. It has also become an Olympic sport and training for that as a sport has kind of become a semi-focus/goal of the style as well. It looks a lot like Karate and vice and versa. Judo - A jacketed wrestling style from Japan. It's Japanese method of grappling that allows the grabbing of the clothes that has its origins from ancient Samurai empty hand combative methods. The style has self defense roots, but is more sport focused and does train around Olympic rules(oh, it's also an Olympic sport). Boxing - Another Olympic sport, but also a professional sport unlike the other two styles before this one. Boxing was a self defense method a long time ago, but has since focused much more on the sportive aspect since then. The style focuses on strikes made to land with knuckles of the fist, and aims hit targets above the waist line. Karate - A traditional style from Japan. Everyone knows what it looks like. Mainly a striking style, though not necessarily limited to that. The style often tries to balance what is traditional and what works, often making what is traditional work in modern environment. Karate also has many different schools and while they share a lot of elements, they are also very different. Personally I like Kyokushin karate out of the bunch. I'm going quickly list few additional style you didn't list in the question. BJJ - a modern popular style that focus on grappling with the opponent on the ground. Before the UFC and mma fighting, a lot of the styles were stand up striking martial art. Strategically and tactically, in self defense you want to stay mobile, which is why you want to stay standing if at all possible which why all these styles were a stand up fighting style. But it also meant all these fighters didn't know what to do if they did end of on the ground. The BJJ takes advantage of that big weakness and allows a person to dominate even an amazing fighter. Muay Thai - It's a kick boxing style from Thailand that allows for punching, kicking, elbows and knees. It's essentially a striking style that allows for all major empty hand weapons to be in play. (Some kung fu stylists may argue that last point pointing out that shoulders and hips are not really trained) MMA - A sportive style that is essentially minimalist on the rules to allow for many different styles to compete against each other. It has since the founding as a sports format to become it's own style combining many elements from many different martial arts.
1) All martial arts is about using skill to defeat size and strength. What would be the point of a martial art if it is all about using brute strength and ones size and you can't use it against someone bigger or stronger? 2) You are confusing names of specific martial arts and names of a class or groups of martial arts. The word "kung fu" as used in Western language means Chinese Martial arts. It is not a name of any one specific Chinese martial art. There are over a dozen styles of Chinese martial arts and that does not even factor in the sub-styles. As for martial arts differs or how they are different, it goes to the history of their origin and how they approach combat. Each one have their ideas or principles which their techniques are based upon. It does not necessarily mean they have a different fundamental precept, but that they may emphasize certain aspects of the theory behind the central idea. One way to look at this is how the science of math has different applications such as accounting, physics, engineering, game theory, computing, etc. but it's all math except different aspects of it used for different purpose. You have basic math, then algebra, trigonometry, geometry, calculus, so on.
If you look them up on the computer, you find sites which will demonstrate some of their stuff, so you can see what suits you from these, for further investigation. I'd avoid those which require several things in combination to work, and those which are more "fancy-dancy" showmanship which stresses "don't actually hurt the opponent, just throw him on the mat" type, but the real, "knock out, disable, cripple, or kill", as most suitable at the time stuff the military teaches. Some of these teach the use of canes (sticks), Yawara sticks (deadly judo sticks), which I trained on, when I found out they require LITTLE TIME TO MASTER, and are VERY EFFECTIVE, but then very one has their own opinions and choices.