Hi, it turned out that is more productive to play in short leagues for gaining of points. If you have a perfect season, you can reach to 7000-8000 points, while if you have a good/perfect season in a league of 20 teams, you can reach around 10000 points or more (rarely 12000.) In addition, neither you don't grab to play against all of 20 managers, because many of them, suddenly quit. So, you can make 7000 points in term of 22 days (league of 10 teams) or you can make 10000 in term of 43 days (league of 20 teams.)
Draw a conclusion!
About codes... they are "pro" managers, as me, as you, with some experience versus, most times, newbies, namely new users or managers which doesn't play at an advanced level (battle between crews, competitions, etc.)