Yes leverage allows you to take more risk, but it doesnt force you too. Money managment and position sizing is the difference between people that use it well and people that blow up - I have done both.
No but you end up taking more risk because you can. Like in your example, if you have 68K in cash in your portfolio. You will only be able to take that one position on CBA. Alternatively using derivatives or margin loans, you will be able to take on a larger position or more positions.
Max possible risk to portfolio in scenario 1, 2%. In scenario 2 up to 100%. The point is not whether you are a good trader or not; I completely agree that you have to be to use leverage properly. But saying that people make 200% and it can be done easily to newcomers like myself and claiming everyone else is a liar is a bit misleading. However you did mention later that you are talking about leverage and derivatives so fair enough. This is not a mute point to be swept under the carpet.
People chasing 200% without leverage or proper understanding on how to use it properly, as you say you have mastered, are bound to shoot themselves in the foot.
Back to the point I was trying to make. It is much better to compare capital at risk as it will give you comparable results. As an example, my current portfolio is mainly cash (Not much of a risk taker and I currently have a very poor understanding of the stocks ). Return on capital would be 5% over the year. Crap right? Return on capital at risk is infinite (X/0.0 = InF; X> 0.0) (well as long as the bank guarantee is on and depends on how you account for inflation). Therefore I can claim I did better than most on this thread on return on capital at risk. Obviously it depends on how you look at things ...