On the placement of laser turrets

There's an interesting question of what the ideal number of turrets is. One thing that's counterintuitive is that the number of turrets has little effect on total firepower. Your laser engine(s) can fire the beam down a central corridor, with mirrors to select a branch toward any of the laser turrets. No matter how many turrets you have, you can concentrate all laser firepower through one turret. (Rick Robinson calls this a "Laserstar")

I tend to favor two turrets on opposite sides. Besides providing all around coverage and some redundancy, it also allows use of a "hunter-killer" tactic. While one turret fires the laser to kill a target, the other turret can be scanning to "hunt" for the next target. This allows a near instantaneous switch from one target to the next, minimizing down time for the laser engine.

More importantly, this has a big tactical effect on the enemy's options. Suppose each of your ships only had one laser turret, and the enemy knows this. Then the enemy knows it takes some time for you to switch from the current targets to new targets. If the enemy notices that all of your ships are firing on particular targets, he can take advantage of this to open up sensitive sensors or radiators onboard the non-targeted ships. He knows that if you want to fire on a different target, he's got enough time to close protective "shutters". In contrast, with two turrets per ship nowhere is safe from being targeted.

This depends on the type of laser, of course. With typical IR-UV wavelength lasers, the availability of efficient mirrors generally makes this a compelling option. You only need one or two turrets for full coverage (or practically full coverage), but you might still include more turrets for redundancy and/or "hunter-killer" tactics (one turret hunts for the next target while the current turret kills the current target).

Other types of laser work differently. In particular, an X-ray free electron laser requires pointing the entire ship at the target - particularly if a widely spaced zone plate is used to focus it (the zone plate may be light seconds away, placed between the beam generating ship and the target).

And yet, even in that case the electron beam accelerator might be multi-purpose. The electron beam can be diverted to turreted wigglers for short range lasers, and the electron beam might even be used directly for various purposes. In particular, the electron beam could be used for ablative propulsion of dumb defensive drones (just dumb rocks vaguely near the ship), as well as ablative propulsion for the ship itself.

I'd say a "spinal mount" is fixed with respect to the long axis of a spacecraft, but the main direction of thrust could be some other direction. In fact, it makes more sense for the direction of thrust to be sideways to the long axis of a warship, or for the main thrusters to be turreted.

It generally makes sense to try and present a narrow profile to the enemy. This may actually be generally impossible when the enemy has more than one warship, so the ideal shape might actually be a reversed cone (a teardrop shape). But when you need a kilometer long X-ray wiggler, such a compact shape may be out of the question.

If you are pointing toward the enemy, having main thrusters pointing directly away from the enemy basically eliminates all maneuver capability. You have one degree of freedom, along a direction which is entirely dependent upon the enemy's maneuvers. Basically, you give up both maneuver capability and forward planning capability.

But having main thrusters pointed "broadside" gives you two degrees of freedom, and gives you the flexibility to maneuver freely perpendicular to the enemy. Even better is if the main thrusters can rotate a bit in one dimension. That basically gives you complete flexibility to thrust in practically any direction regardless of the enemy's maneuvers.

That's assuming you have something that looks like traditional thrusters. If your main thrust comes from pulsed ablation/spallation of the ship's main armor/hull, things may look very different anyway.