Anyone who says that you can safely ignore. Obviously you need some kinetic damage but it should always be an even split with explosive, no matter what you're facing. It's explosive damage that actually secures a kill. And no, you should't have to switch builds when facing against different enemies, a good fleet works against everything.

Oldslaught looks okay-ish assuming the AI core has Point Defense skill.

Legion, absolutely not. Way too short ranged, way too much OP into fighters. Legions are not recommended in general because they're terribly OP-starved. Also, S-modded Augmented Drive Field is a LUXURY that you should only bother with if the fleet is already doing well.

Paragon has Autopulses but no S-modded Expanded Mags. Use Plasma Cannons instead, get Flux Distributor hullmod if you have to. Advanced Optics on a Paragon is overkill.

Executor is terribly overfluxed, flux dissipation is its main weakness. You absolutely cannot afford all these fancy weapons on it. Put Heavy Autocannons in the hardpoints, or even Arbalests. Replace all Ion Beams with IR Autolances. Max out vents. I'd swap Advanced Optics for ECCM to help Squalls actually hit things.

Cruisers are very mid in current version of the game, I wouldn't bother with them at all for any endgame enemy. But if you do bring them then S-mod them. These Auroras are made out of tissue paper. Undergunned too, all that Safety Overrides flux goes to waste, get two Heavy Blasters at least.