I'm early in the playthough myself (finished Vulcanus, now on Fulgora). So far I've used HMG and Gatlings. From my experience, correct placement of the turrets is crucial - because these turrets have so much range, wide arc backline variants waste ammo by shooting asteroids far to the sides of the ship, asteroids that would never hit your ship in the first place. On the other hand, frontline variants (especially the Gatling) pointed to the front clear asteroids so far ahead, you can reach much, MUCH greater speeds and still be safe.
-- Further notes are predictions, since no personal experience so far. --
Cannons, unless you're willing to import ammo from planets, are completely unusable on platforms. Since ammo takes both Explosives and Plastic to make, making them on platforms needs Coal Synthesis from Gleba AND Coal Liquefaction from Vulcanus, with a convoluted production chain (Carbon -> Coal -> 3 Oils (Liquefaction) -> Petroleum (Cracking) -> Plastic -> Ammo). If you DO somehow manage to make ammo in-situ, damage and range is high enough to theoretically allow you to get to Shattered Planet without needing Railguns to crack the biggest asteroids.
Cruise Missile turrets, I have no idea. My guess is fire rate is too low to be useful, since these turrets only advantage over stock Rocket Turret is vastly increased range and potentially limited firing arc might be useful too.
Pulse Laser has the same problem as stock Laser Turret - medium+ asteroids have high damage resist (90%+) against Laser damage. Only useful in combination with bullet turrets to clear small asteroids after guns have broken the medium ones, to preserve bullet ammo. Should be decent when used with 1 or 2 Backline HMG set to only shoot medium asteroids and let lasers do the cleanup.
Thermal Laser turrets are completely useless, all asteroids have 100% resist against fire damage.
Backline Beam turret is useless damage-wise (all asteroids have 100% resist against electric damage), don't know if slow effect works.
Frontline Beam turret - now this one is interesting. Asteroids, inexplicably, have 0% resist against POISON damage, which this turret utilizes. And this one pierces all targets in a line up to 40 range as well. Will need a couple of laser damage techs to truly be effective, but should work very well at least for the 3 starter planets for resource free asteroid clearing.
For planetary work, cannon turrets do REALLY WELL against Demolishers when using regular, non-explosive shells, reaching between 5k (Light and Heavy) and 7k (Dual) raw DPS per turret at yellow tech level. A decent cluster of Dual and/or Heavy cannons should make short work of even Big Demolishers. There's a reason Heavy Cannon turrets are unlocked on Vulcanus.
For Gleba, Thermal Laser turrets would be great - one hit guarantees a kill on any Strafer with the fire DoT. Requires importing these from Fulgora.
Backline Beam turret (or Cruise Missile with Slowdown Rockets) would be great at keeping Stompers away from defences for longer with the slowdown.
In fact, the Nauvis strat of building a perimeter wall should work just fine here, thanks to massive ranges on most of the modular turrets. Just keep contingencies, limited firing arcs means Gun Turret backup is required here, a Stomper managing to live through would wreack havoc.
