Regarding turrets, I have used them quite a lot, but only on large ships with lots of hardpoints. I usually just keep one or two "main guns" that I control directly, and use the turrets to keep the pressure up as I'm moving the ship around to face the enemy. When I get them in front of me I let go with the main guns.
Here's my Corvette build. It's nearly indestructible in PVE. I'm a terrible pilot, really, but I win all my battles in this thing.
A ship builder, outfitting and comparison tool for Elite Dangerous
s.orbis.zone
I also have a T-10 that uses ALL turrets, no main guns. In this case I use the SLF as the "main gun" and instruct it to attack my selected target. This then causes the target to become hostile, which then causes all my turrets to fire at them (I have them set to "Fire at Will." All I have to do as the pilot is maneuver the ship to keep the turrets more-or-less lined up. It's fun and effective in RES sites and excellent for doing pirate massacre missions, which is mostly what I use it for (but this ship isn't going to cut it in a Conflict Zone, it's more for relaxed "goofing around" combat).
A ship builder, outfitting and comparison tool for Elite Dangerous
s.orbis.zone
I'm also annoyed by PIP management, so these ships are designed to work with 4 pips in Shields and 2 in Weapons (and zero in Engines). I almost never move them. It's the lazy man's way of combat
I'm sure that the turrets have less "DPS" but I don't care. I win easily.
So that's my take on turrets.