Yeah it doesn't matter where you place your players on the tactics page, defenders are just defenders, midfielders just midfielders :p
You will pick it up but the game does seem to favour a strong midfield which is why most people opt for 3-5-2 and 4-5-1. Most teams have a home advantage but it's not standard, some teams will perform better at home than others and some teams are better away. There's a reason why the Xpert slogan is 'easy to play, hard to master'.
When you pick your match line up you want to pay attention to teamwork values, form, strength and average age - but most importantly DV. You need to keep your players in high form and they need game time or they will not raise in skill. Look at your opponent's team and try to anticipate how they will play, think what you would do with their team against yours.