There are a myriad of ways to succeed, everyone is just giving their own opinions. To each their own. I think it's important to find a style that works for you, that you can maintain, and do it. Honestly, one of the top indicators of success that I have seen is life experience, which you can't get over the summer. I only know personally four people in the top 10 of the class (not percent, but top ten), and all of them have over 5 years of work experience.
I support those who say do as much 0L prep as possible, including the E & Es, because it gives you a very good overview of what you're going to learn. I've never found that studying a map before going on a trip is a bad idea. I see no chance that any intelligent person will let anything they learned from before law school trump what they learn while in law school. All it can do is give you a good idea of what's coming and a decent background of knowledge, because experience is always the best teacher.
There are people who do very well and don't use supplements at all, and some of them will even tell you they don't do much work outside of class, but what I think you will find is that they engage the material daily. Even if they aren't crafting outlines or doing extra work, they are having daily conversations about the law, they are having real arguments over the strengths and weaknesses of theories and cases. In effect, they are using the material in a way that will reinforce it in their minds.
Most people who get to law school just don't work efficiently. They may stay in the library all day long, but they spend a majority of that time chatting with others. So even though they may tell you they've done X or Y, or spent so many hours a day doing something, that may not be a helpful comparison. My point is that you can't give a blueprint for success all the time, but there are very few successful people in any area of life, and I think law school is included, who will say that preparing was harmful. It's kind of like Pascal's Wager, in that the loss from not preparing is far greater than the loss from preparing, assuming your choice was the wrong one. If you make the decision to go to law school and have decided to do just enough to get by, then you don't even need to be reading this thread. If you really want to do the best you possibly can, then it means you're going to have to work hard, and put in the time. And some of that work and time will end up being wasted and useless, and you will look back and realize you didn't need to do it from the beginning. But some of that time will be essential, and out of 100 pages of material you may get three or four valuable tidbits. If you're good enough to be in the top 10% of your class and do no prep and not work that hard, then imagine how well you could do if you actually DID the prep and the extra work.
You have to measure yourself against how well YOU can do...and then decide how much you want it.