I used prefolds, terry flats & covers at the start. They are great, cheap & fit all babies
Also awesome for back up once you start to fill your stash.

Maz covers are the best. No doubt Fit over any nappy IME.

All brands will fit differently, so I'd wait til bub is here to invest alot of money. That way you have a chance of knowing what fits best

I have 21 AIO's/AI2's & wash every 2 - 3 days. I have flate & prefolds I use in there too. I'd say 10 - 12 or more a day for the NB stage. You will be vhanging every hour or 2 day & night.

ETA - I don't use powder. If I do I use eco store. DD gets eczema from washing powders.