Having league leaders does increase your merchandise. But the difference isn't going to be huge, maybe a few thousand.
Playing "ugly" offensive tactics does not directly affect your merchandise money. HOWEVER, playing "ugly" offensive tactics means you might be more likely to lose and if you lose then it can lower your merchandise money, and also playing "ugly" offensive tactics can make it harder for your players to score lots of points and so it can be harder to be a league leader and hence your merchandise will not go up.