Yes, they 100% do bring out unique archival records for you to review. It's one of the neat things about going to the facility!

Sometimes if there's a more extensive process to retrieve the record (i.e. your archivist has to talk to a different government entity or agency to get the information) you might get some facsimiles, but often the information is only captured in the physical document that you're looking at. Moreover, to reiterate my point from above, part of the reason that College Park is making this decision (probably) is because it takes time and coordination to get these documents, and they want to ensure that--with limited staff and resources--they're still able to fulfill their mission of providing access to information.

Most of the records that exist under NARA's purview are not backed up at all. There's a major initiative to digitize existing holdings, but that's challenging/fraught with staffing issues. It's basically an under- or un-funded mandate.

If you're interested, there's been a fair amount of theft throughout the history of the agency, and they actually maintain a page on it: https://www.archives.gov/research/recover/notable-thefts.htm...

Can't speak for the US National Archives, but I do occasionally head to the National Archives of Australia to look at things that pique my interest, and I can confirm that yes, you can just ask for entire folders full of documents and in most cases, they'll take the originals and just plop them in a plastic tub for you to pick up and have a read through. It is a slightly strange feeling opening up a file and flicking through correspondence that was once personally handled by a Prime Minister from 100+ years ago. (They will use scanned copies for anything that either can't be handled for conservation reasons or has been redacted for security reasons.)