You got to be able to play through the middle, you will want midfielders with good rates for going up and going back, and being able to pass the ball. You need your players to have good passing so you can keep possession. The central CM position I always put a strong player in that position who has more of M/H work rate so he sits more.

I make the ST's quick and make sure they have good W/R such as H/L so they make runs constantly.

A lot of passing round the middle.

Then as soon as you see the 2 STs making a run, play the over the top ball to them.

what workrates are best for defenders?

RZDY wrote what workrates are best for defenders?

You can go with H/M on your LB and RB,

Then M/H, or even better L/H on your CBs.

for the 4312 I recommend a juventus midfield, vidal pogab pirlo

all very good players but each specialise in a area

vidal- Defensive
pogba - Attacking
Pirlo - Passing

I really like playing with the 4312 formation and I found that the 3 CMs are make or break for this formation.

Because the two wide CMs will work sort of like RM and LM you need to have H/H Workrates on both (Vidal and Marchisio for example). The middle one needs to be a defensive minded player with at least M/H (De Rossi is my man)

I hope this helped you out! In terms of playing style, you will need to pass a lot through the middle and maybe go wide sometimes, but keep your fullbacks back!

You want to set Instructions on one of your central midfielders to "Stay Back".