Its just a personal preference, but I prefer to use dual heavy cannons and turrets on my escort ships for that extra punch.
Note that Tactical Team, Engineering Team and Science Team all share the same cooldown timer. Which means if you use any one of the three abilities, the you can't use the others for quite some time. For that reason, I tend to stick with only 2 Tactical teams and no science/engineering teams. I also like to have two Emergency Power to Shields as they not only provide shield regeneration, but also reduces damage for 30 seconds.
As for KDF carriers, I have never played them so I can only provide general tips. Rare blue fighters from the dilithium store performs better than the uncommon green fighters. Also, not all fighters are designed for causing damage. Some are designed to drain energy, others disable subsystems so choose your fighters wisely.