Not every student at Stanford was a 4.0 - even if you exclude the ‘hooked’ applicants. So a B isn’t going to prevent you from getting in anywhere (and yes, it will show up on your transcript.)
On the other hand, attending summer camps every summer not only won’t help, but will probably hurt. Lots of kids go to summer camps. It doesn’t differentiate them in any way except to prove that their parents have enough money to pay for camp and they don’t have to work. Which isn’t to say all camps are bad - take one if it’s in an area of special interest to you and no, going to a Berkeley camp won’t matter at all if they are offering what you want. And ‘effort’ is not going to get you in either. Every student who was admitted - and most of those who applied - put a great deal of effort into their education and ECs.
Rather than wasting your time worrying about what Stanford will think and will they notice if you do X, focus instead on what you like to do and are good at. Do things you really enjoy (just a few, not a half dozen), and figure out how you will get the most out of those activities. Not only will your life be better, but you will be a more interesting person to be around - and maybe the adcoms at some top school will decide they want you to be around too.