Polaroids are a little too expensive for my tastes but are really interesting from a historical/technical point of view so I am unlikely to use them,although I'm glad that they are made again (if that makes any sense) but from what you are saying a photo automatically loses quality when it is printed because of the printing process so trying to enlarge it would only enlarge these imperfections ?
Poleroids historically came in rather low quality 'consumer' grade, all in one cameras, or they came in very much higher quality 'professional' grade camera-backs for things like Bronica or Hassablads's etc. So there's a huge disparity between the two dumbbell ends before you begin.
As has been mentioned; Lands' instant picture process, was rather compromised from the off, and produced relatively small size prints of lesser image quality than could be made conventionally from a negative.
Then you have the matter of scanning; and the possible variation there is enormous, and starts with how good the print is before you start, which depends on the camera, the film, and more, whether it was well focused, composed and exposed and what the contrast range of the scene was.
Debate over scanning from neg and scanning from print, has raged since digital imaging started to become viable; And as also already said, its VERY much down to your own ideas of acceptable image quality.
My very first digitized images were made on a sheet-feed scanner, around about 1995.... I had to buy two bulk boxes of 1.44" floppy diskettes to scan a pack of photo's from boots! I got about 1-photo per disc (1.2ish MB! And 40Mb needed by a pack of photo's from boots would have FILLED a 'big' 40Mb hard drive of a computer of the time!) & ISTR that the scanner boasted I think a 300dpi resolution, which ISTR I had to down-rate to probably about 150dpi to save file size and time to make the job even viable.... but would have given me about a 10Mpix file out-put... that I have to say was pretty impressive in 1995! Was still impressive when I got a dedicated 35mm film scanner in Y2K, and remained reasonably impressive compared to direct to digital SLR's until a way past 2010.... Taking around 4-hours per photo to scan, with a pretty high end for the time IBM 486 computer, with 'enormous' 4Mb of memory, though, wasn't! Lol! Not that that particular issue has improved all that much, even with duel and quad core processors! But still.
Point is that you CAN get some pretty impressive resolution scans from prints; even with a pretty low resolution and wobbly sheet feed one of old, and the limitations of the original image, and the print quality or its age degradation will likely become the biggest limitation long before the scanner starts to add any; then it's a question of how 'good' you need or want the digital reproduction, first on-screen, and then if you make a computer generated print.
Many have 'enlarged' black&white 6x6cm contact prints to A4 / 10x8inch on a common office photo-copier, and got something good enough to hang on the wall or put in a frame on the mantle-piece, most folk believe is still a 'wet' photo-print, not a photo-copy, if behind glass....... that's around 4x enlargement from original, and gives a rough guide to how much enlargement you can apply.
With old prints, B&W tends to suffer less degradation than colour, and is more easily salvaged or restored, and you have some greater tolerance to enlarge; but it is so much dependent on the original print.and ultimately how good you want it in final repro.
Net 'lore' about scanning Polaroids is then very very mutable, vagaries and variations, and reasons for that are just endless and defy any meaningful generalization; other than, Polaroids are, compromised from the very start compared to 35mm or Medium format negative, so how good do you want or need, and if you want high quality and potentially larger images, Polaroid ISN'T the ideal place to start... but in a world of compromise? Which ones are you happiest with?
Scanning 'archive' Polaroid media, its your only option really, and dropping one on a modern flat-bed, with a high dpi count, you can get an enormous pixie count, and pixel peeping you can quickly find the flaws in the original media.. but shrink to more moderate pixel / file size, and view at more reasonable enlargement, a lot of that will likely disappear.. play in photo-shop to your hearts content, but how good and how big do you really want/need? It's do-able, and you can recover and revitalize a lot of old photo's if you try hard enough, but you'll never make a silk purse out of a sows ear.
Have you any idea which films produce a negative ?
From wobbly memory, none of the consumer 'cartridge' Polaroids for dedicated Polaroid cameras made negs as well as prints. And I think most of the polaroid backs for Med-Format cameras usually used the same cartridges; The only set-up I recall 'may' have produced negatives was the 35mm black-and-white polaroid system, that was a bit of an odd ball.
From memory, again; the 35mm B&W Polaroid system, didn't make 'instant' photo's, straight out of camera; you bought a 35mm cassette, ran it through 35mm camera as you would any other 35mm film; then instead of taking it to boots or into the dark room and cracking the can; you had to pop it into the Polaroid Processor machine, to get tiny 1x1.5" Polaroid 'contact' prints out of it, and you might have got the original negs on the backing paper. Some 'pro' cartridges may have worked similarly, I don't really know.