Hi Atir, thanks for your interest!
We've written a couple of blog posts on the subject of performance with Construct 2:
HTML5 2D gaming performance analysis (note: some results are out of date, performance is even better now)
IE10: "fast" and "native" has gone to other browsers
Optimisation: don't waste your time
We've also just released support for CocoonJS and appMobi's directCanvas to significantly boost performance on mobile (up to 10x faster).
Code editing is a regular suggestion, but we are really here to make a tool for non-programmers... maybe we'll branch out to code in the future, but it's not in our plans for the time being.