the biggest difference in my opinion is that in FM21 once a player makes a decision, he is going to carry on a do what he has decided even if the circumstances has changed that is why you get wingers and fullbacks that once they start running with the ball they don't stop even if they are running into 3 players. In FM 22 on the other hand when it lunched in the blog there was a portion that talked about "slices" and basically the fact that now players can change their decision if the condition is no longer favourable to what they initially wanted to do.
Another thing is you have some roles that play slightly differently in FM like the IWB, IF, IWB and the fact that even with poor teams it's much more easier to hold on to the ball compared to FM21 where they would just kick it long if there was a threat of them being under pressure.