Can someone explain to me transfers during a season?
Can you change players as much as you want in a season?
Does it matter where you position your players on the pitch?
Does it matter who your captain and vice captain is?
You can make unlimited transfers up until the season starts. During the season, you can make 2 per week. If you make more than 2 in a week, you'll be penalized. You also have 2 "wild cards" - one for before the January window, one after - that you can use to make unlimited transfers in that week.
You can change your starting XI and subs as much as you want.
Doesn't matter where your players are on the pitch.
Captains do matter. They get increased points, so choose wisely. Best bet is to make your top striker or midfielder captain (for example, my captain is Aguero and vice-captain is David Silva).