High defensive line means that when opponent has the ball, your defenders will push forward, making less time for opposition players. Basicly it attempts to reduce the space opponent has, if the defensive line is 20m lower, then there is bigger gap between defence and midfield, so easier to pass to feet of the strikers/midfielders going forward. There is also risks, iffor some reason opposition player has too much space and your defensive line has pushed higher, there is loads of space behind your defence, all it needs is a quick striker running to that space and pass to somewhere there.
If you play more wider your players will play more wider, thus spreading the play and leaving space to the middle when opposition players have to follow your wingers to wide positions. More space in attacks, but when you lose the ball, there is many gaps that opponent can exploit with a quick counter attack. Basicly if you are weaker team trying to defend well and not concede, then play narrow, it is harder to break down. If you are stronger, then play wider, to spread the play and make more space to your attacking players.
Run from deep tells you how often player will leave his position to go forward. As an example I currently use tactic which has 3 central midfielders. One of them has run from deep set to rarely, others sometimes, and when it attack, the one who has run from deep set to rarely stays much lower on the pitch, acting almost like a defensive midfielder, while the other too go forward far more often.
Don't know why I wrote this long post, hopefully it wasn't for nothing...
