Re: Alva NB's?
The snap newborns don't fit most newborns very well, they don't get small enough, but the velcro newborns are much more adjustable, and you can even fold down the front and velcro to the back, so they get really small.
As far as stuffing them, they keep tinkering with the design. I got some custom velcros in January and the crotch is wider and they are easy to stuff. Much easier than my XS FuzziBunz with that *^%%^ sticky PUL.
If you buy new velcros off their website, you'll probably get wider ones that are easier to stuff, but the snaps sound like they are still hit and miss on width. Anything used is probably going to be narrower and harder to stuff.