If you haven't modified any of the layouts, it's easy to find the difference between the stock layouts and OFM9G. Simply navigate around for a minute, then revert back to the original layout and try doing the same things. Because the layouts are different you'll quickly notice it. Don't do that if you have made a change with the layout editor unless you back up first because it's annoying to have to redo a lot of changes… that's from personal experience.
OFM9G is good, but so is the stock layout. Some people like one, others like the other. The nice thing is it's easy to bend them to your will. My FM9 layout started out as OFM9G but now works exactly how I envision it.