I'm a fitteds and covers girl for NBs. Their poos are really no match for AI2s or pockets in my experience and 2 layers of leg elastic works like magic. I know they aren't for everyone, but I preferred adding a cover to changing a whole outfit.

I love Bubblebubs for tinies. Lil Daks make tiny pockets that fit well and BBH make littler nappies that fit but I hated them.
I found OSFM didn't fit properly until about 4 months old, even on my 4kg at birth kiddo.
I would also advise against getting a stash made up of only one brand. Would really suck if they just didn't suit your bub. All of mine have been different and suited different nappies.