If you are going to do any racing beyond a hobby, meaning something with a rule book, then keep the book with you, read it, read it again, memorize it, sleep with it, and then build the car to those specs. Autocross, and touring car racing have extremely focused groups. Build the car to fit one of those classes and stick to it. If you want to dabble in both with the same car, then you need to do twice as much reading. Build a car that can adheres to the strictest requirements and then you may be okay with other forms of racing, but at times, tires, sway bar sizes, roll cages, all can bump you into an entirely different class. Autoracing is usually not a one car fits all type of thing. I would suggest you narrow your focus to what you REALLY will actually be doing and then build accordingly. Right now It sounds like you are more of a hobbyist who wants to try a bit of everything for fun, which then build the safest car you can and have at it. But building a car without a clear focus on what it will be used for almost ensures you will build the wrong car and spend too much.