When editing a post in Mastercam you must and i will repeat must always save the original. So that any changes you make, you can and will always be able to go back to the original. Mastercam will supply generic post's and will also modify a post to your specific requirements on request.
I would not recommend editing the post to extensively because this may be detrimental to your machine function. But after you are EXPERIENCED with the system, you can then SURF the code to determine what line and post code to change/turn off/turn on to suit your machine function or preference.
Always proof the post edits before sending to the machine. And then always proof/single block the complete program to make sure your changes are functional.
Because we all know that at full rapid you can not hit the E STOP quick enough.