I´m sure that they did not use any Digicams back in the 30´s
The quality and how big you can digitize these pictures depends on how good they survived over tha last decades.
They can scan celluloid movies from the 40´s up to 4k if they are in good condition.
So.. HOLY CRAP is all I can say here.. I don't know what size ordered prints are, but there is a wealth of incredible pictures on this site: Schlegelmilch Photography.
I just put in 1969, and there's 532 pictures. All high res, most of which are outstanding. I could spend years here.
I think I read somewhere that if you order high-res images (digital images, not prints) they will be A5 size at 300dpi, so they're a fair size. Not massive, but decent.