That shorty exhaust does look good.
I tell a lot of people that get on 600s, it gives you enough power to make bad decisions. If you've spent some time on a 300, you're likely not trying to figure out how to roll the throttle on correctly. You're probably not going to loop it just from starting, or badly miss shift. What could happen, is you'll love the feeling of the power, and you'll go too fast, and you won't realize how quickly you're covering ground, and when someone pulls out of a side street you realize too late that you cannot brake enough to avoid them. That's just going too fast for conditions, and it's not an accident, it's a poor decision that the bike gave you the power to make. Similarly, if you go into a turn too hot, because you were riding quickly, same story.
That said, it sounds like you're on the right track. Stay within your own limits, determine which skills you want to improve, and make a plan to improve those things. This gives you the freedom to focus on one new thing at a time so you can begin to build on what you know now.
Also, if you do ever go into a turn too hot, just turn your head, look where you want to be, and trust the bike. You'll make it.
Never ride faster than you can stop