I'd say your average game will not be so different. People tend to group up a little better, but still not too well. Individual skill level somewhat better, team play still mediocre. NASCAR still alive. You'll still see a mixture of meta boats and non-optimal fun builds.
One distinct difference is that at T3 you'll occasionally face T5 guys, while that's strictly not possible at T2. So the absolute worst terribad behaviours will vanish.
But as far as the typical game where you mostly face T2 people vs. T3 people earlier, not a huge difference. You'll need to be a little more careful, as you'll be punished a bit quicker for errors.
Edited by jss78, 23 March 2016 - 10:03 AM.