I think if pocket dipes are working for you, then you should stick with that.
As for Types. I'm sure there are plenty of websites to break it down for you, but I don't have any links.
Here is my take on it.
With fitteds, the benefit is that you can control the material going right up against the baby's skin. You can use all natural cottons or bamboo's. You still need a cover but you don't have to worry about pinning or using a snappi with these because they go on like a regular diaper. You can get these with snaps or Aplix. I always recommend Snaps.
I think for the NB stage, I prefer all natural materials like cotton against the baby's skin. This is what I recommend. You never know if your baby is going to have a sensitivity to polyester.
With Pockets diapers you've got polyester up against the baby's skin. Some baby's are allergic.
another benefit to fitteds, prefolds, wraps..You can wash them separately from the covers. If your baby gets a rash and you need to use a cream, it's easier to strip them or use a bit of bleach. If you baby gets a yeast rash, you can use a bit of bleach...just a bit. and then rinse , rinse , rinse...You really can't do that with Pocket dipes because of all the cute colors and prints.
Last but not least...
Fitteds, prefolds, wraps...this is cheaper then doing Pocket, AIO's and AI2's. Don't get me wrong...some fitteds can get pricey, especially when you start buying the dyed, Hemp bamboo stuff, but generally speaking, it's the most economical way to go.
Clear as mud?