When is this a good bait to use? What kind of baitfish is needed for this to be at its best 

Doesnt need to imitate anything really.  Jumping shad or a bluegill chasing bugs on surface.

 

Ive caught a couple decent bass on them but havent figured out best time.  Usually like throwing it in windy conditions due to size and noise.  Ive caught them on flat water though but it can be overwhelming.

Just about anytime you'd throw a Pop-R, but not throwing to targets.There is just no way to set these down softly and that splash usually spooks 'em. If you can throw past a target and work this bait up to it, you'll be surprised and the violent blow ups you'll get.  It's a good alternative for a prop bait in turbulent water, too and you don't see many guys throwing them here in the mid-west.

Yeah I ask because I seen them only do good at Blueback herring lakes it seems

Good to cover big flats and open areas mainly because they cast a mile and make a good commotion that draws them up from deep water if needed. I do like the smaller Showerblows for targets because it turns so sharp that it almost sits in one place and can really annoy a fish into biting.