Cheat sheets are there to sort of, sadly, dumb down the course. but in reality, if you have studied thoroughly and practised everything, then there's really no need for it. never go gaga about putting everything in them, just the relevant formulae and then some concepts that you feel weak at, if any.
As for studying, im not gonna deny it but i lived off external lectures. studying vce phys is extremely easy. doing well at it, and being in the top 7.5% is extremely hard. (some) lectres give you an edge towards exams because they give you exam strategies and better notes. but it will still be up to you to perform well in your sacs and especially the exams. also, dont make the mistake of doing too many commercial study books like checkpoints, etc like i did for the first exam. go around this site and look for as many 1/2 or 3/4 exams as you can and do them instead under STRICT exam conditions.
Lets face it. vce isnt about knowing everything. its about beating everyone. the more exam strategies and traps you are exposed to, the better off you are in the end.