I play with a team in the Argentine league (Newell's). The season is split in two in Argentina, you have the "initial" league from Aug - Dec, and then the "final" league from Jan - May/Jun-ish.
They have two European competitions - the Sudamerica and the Libertadores. I'm not entirely sure how exactly you qualify for each, but the Sudamerica takes place in the first have of the season, and the Libertadores in the 2nd half.
Gameplay wise, it's not really much different than playing with a European team. You can still sign the same players - though I'm trying to buy more South American players in general.
I'm not sure how it works if you were to pick a Brazilian team, or a team from another South American country. So, if you want to know who to pick..... errrm...... pick the one with the best kit.