Should I mix different turret types?

Usually not.

Turrets that rotate at different speeds and have different optimal ranges are harder to keep on target.

• Every turret of one family joins one battery; a different family forms a second battery.
• A battery takes its damage, ranges (optimal and falloff), tracking, crit chance and cycle time as the average across its turrets.
• Each family gives its battery one ability, such as Rapidfire on the Auto-Cannon or Charge Shot on the Railgun.
• You can fit at most six turrets of one family, and no more Battery modules than the hull has battery hardpoints.