Can I NOT roleplay in CF FL? Are Weapons compatibility stuck to specific ships like in Discovery?

As I understand it, we do not have weird weapon customizations like Disco IE: Disco weapons have class 6-9 fighter weapons and other random stuff whilst Crossfire has gun weapons from 1-10 for fighters. Captial ship weapons come pre-installed on these (Except for Battleships/Dreadnaughts). On Crossfire, you can pretty much have all the weaponry you can find to put on your fighter (Excluding Custom NPC Weapons like Alien turrets and DK Pulse Cannons)

You can buy custom Battleship Turrets at any place you can buy a Dreadnaught or Battleship. I'd recommend the Double Barreled Civillian turrets as they fire two shots instead of one from the same turret.

Hth

Actually, you can buy Battleship turrets only on House capitol planets (Manhattan, New London, New Tokyo, New Berlin and Murmansk) and Crossfire Docks. Each of these bases sell only their turrets (e.g. Crossfire Docks sell Civilian turrets, New Tokyo sell Kusarian turrets, etc).
Battleships themselves can be bought elsewhere (aside from Crossfire Docks). For example, Liberty Battleship - Iteron can be bought on California Minor, but it has no guns out of the box so you'll have to fly without guns to the place where you can buy them.
At least Iteron - and Osiris, and Liberty Dreadnought - are immune to cruise disruptors.

As about fighter weapons, only class is any hard limitation. For most VHFs it is generally assumed that you can't go wrong with Coalition Gatlings filling class 10 slots and class 9 gun slots are best taken by Nemesis and Cataclysm missile launchers.