Until you CD your specific baby, it's hard to know what will fit best and what you'll like best. If it were me I'd register for (and ultimately make sure I had) the NB stuff you've mentioned and maybe 12 small prefolds plus a couple covers. You really can't go wrong with prefolds and you can always use them as doublers in pockets.
When LO gets close to needing smalls (around 10-12lbs for us), I'd do a diaper trial to some place like Jillian's Drawers. (You can register for a gift card to do this.) The trial lets you try a fitted, some prefolds, a few pockets and a AI0 or AI2. That way you can try lot of different styles and brands to see what fits LO and what you like best. Then you return what you don't want to keep and can buy more of what you like. Also keep in mind that what fits well at 12 pounds may not fit as well at 18 pounds. So get a variety of brands.
Good luck & have fun building your stash!!
Oh my gosh! I just had a revelation, and now I feel like such a dork! I didn't realize that a fitted came with the Jillina's trial! Now I know why there was one pretty blue diaper with snaps that leaked every time. I thought it was an AIO, but it was a fitted and needed a cover! Argh!
OP, I think I would probably register for the NB stuff you mentioned plus a few OS pockets, covers, and AIO. It would be like doing the trial, except you would know exactly what you're asking for. Also, some registries give you a discount to buy anything that hasn't been bought for you when you get close to your due date. I know that Target and BRU both do this, and I was able to get 12 Charlie Bananas for around 20% off. I do also recommend the trial, though.