Some of the stuff I've read here now scares me quite a bit to be honest, but I see where it's coming from. I did my initial training on 152s and 172s, later twins, later instruction, the turboprop, and now jets.
Perhaps the most important thing I've picked up from this progression, it's the following: do what it says in the book.
There is a very good reason why the aircraft manufacturer has given you the required procedures, speeds, charts and described the techniques for operating the airplane. They built it, they know how it works, and their test pilots found out what it will and won't do. It does what it says on the tin, it really is that easy.
Now this does of course not exempt you from using airmanship, knowledge and sound judgment to fly the aircraft according to the conditions and your own skill level. Obviously, smaler aircraft do not have the same comprehensive manuals larger aircraft have. However, the manufacturer's procedures should be your starting point, not some made-up procedures that your 300-hour GA instructor told you, because that's what his instructor told him, and that's what his instructor told him before that. (I myself have been that instructor, because I did not know any better at the time.)
As you gain experience in a type, you will learn what the results of procedural deviation will be. As an example, you will learn that it is certainly possible to land a C172 with an approach speed of (let's say) 80 knots, but you will also learn that the landing attitude, the timing and feel for the flare, and the landing distance will be very different. My point is that this should not be your starting point - start by doing it the way Cessna (or whoever designed the plane) wants you to do it, then go from there. Not the other way around.