The screen used ones were not latex, if they were you would see flexing and possibly warping when turning their heads depending on the actors head size, similar to how the original Halloween mask was used in Halloween 2 but looks completely different because dick warlock had a fat head. I'm not sure if they were resin or how thick, but they were 3D printed, there's a video showing the process. The one Heath removes was a silicone copy made specifically so it would look like a cheap latex mask and not have a hard stiff look, silicone was used becauseit forms to the face and half mask versions can be removed and keep its shape, latex over time if not stuffed and stored properly will not keep its shape. Here is that silicone mask, and the link to the 'making of the masks' showing the 3D printer drilling them from solid blocks of resin or maybe thick pvc, but definitely not latex or there wouldn't be any files as the would have been sculpted by hand. As far as I knew, there has never been any files 'found' or 3d prints of them. You can easily tell by simply looking at the various shapes, mouth droop, ears, cheek and edge smoothness, and other small details. Or, take a photo of one that is claimed to be a scan of the hero mask, and overlay it over the hero mask and change how opaque it is and if they don't line up exactly, which they should if they were from the same files, then its not a scan from the original. And it definitely isn't the Chinese knockoffs, the mouth is waaay off.
That video shows the initial masks being 3D printed then a mold being made of that print. The masks were made in said molds. You can see they're rotocasted because the flashing is still attached when they're painting them. They were definitely not 3D printed. They used a stiff vinyl or latex.
You just said they were 3D printed and molds made from that... meaning the sculpts were originally 3D printed, not sculpted by hand. You can clearly see throughout the video the plain white unpainted masks have no flexibility, not even when sat face up when they're painting the gold under the eyes of an unused mask, nor do they have any imperfections which would be very difficult seeing as they would have to cut each hole from eyes to nostrils to mouths. I have several latex and resin copies and latex will flex just by tilting your head and definitely will when handling them or wearing them; which I didn't see at all with any of them during the heist scene, even when the Joker nods his head there is no flexing of the chin or cheeks, not to mention the molds look to be silicone, which won't work to cast a latex mask. As for vinyl, that would have to be very thick or it would be extremely easy to crack. After seeing the masks on display in person 3 different times, none look like they're latex nor looked any different in their shapes or finishes, which you'd expect to see if they were latex as it's a natural material that naturally breaks down, *especially* when worn with sweat and moisture getting inside. The blanks in the video look like blank dull resin molds, especially when it shows the line up and a few need trimmed, which would be way less risky with a resin copy vs pvc. Now pvc or a thicker plastic I could see, but then I would assume they would have made vacuum formed copies instead of a silicone mold and latex I would assume they would have sculpted, especially since they would have needed a casting of each actors head so the latex wouldn't stretch like the example I gave with the original Halloween and Halloween 2, same mask, different look due to the actors head sizes, compared to the Halloween remake where Tyler mayne had a head casting done so the mask would fit him perfectly and keep the intended look, but, after shooting to keep that shape it has to be on a shell cast from his headform, which is why mask collectors stuff their masks with bags; lay one on the ground for a few days or stuff it in a box and watch how easily it looses its shape. Compare the look and worn shots of latex copies like Ministry of Masks, and resin copies done by Taylor Jean. Here are 2 pics of his resin blanks of his limited run of 'happy' replicas. A thick plastic, maybe, but I definitely don't see them as latex, especially as a mask collector myself with masks from vacuum formed vintage masks, abs hocks, resin, latex, and silicone, in person they looked like resin. Definitely could be a form of plastic, but I definitely don't see latex at all, especially with the shapes and well defined cheeks, brow lines, and the slits in the mouth. In fact, that's the entire reason I wear a resin copy for cosplay and not the ministry of masks latex version, because it will bend of distort not only based on head size but head movement, and is surprisingly just as heavy if not heavier than the 3 resin copies because the latex had to be cast thick enough so it would keep its shape and flex less.
You can punch hair in resin.... that photo above of Taylor's copy has punched hair in it , it's a resin sculpt. You only have to mold it in the sculpt or drill small holes. When done with latex or silicone, that punching would be much tighter.
Here you can see one on the left with the hair draped over it and is clearly heavy enough to sit backwards instead of falling forward, same with bozos although he does seem to have some trimming needed underneath along with the other 2 on the end, not going to be easy with a thin plastic or vinyl, which I'm wondering if you can explain as they're both essentially a type of plastic. If you mean vinyl as in how the older vintage masks were or like the 2019 Joker mask was, that will definitely crack before you can trim or punch any hair into it. I own 3 vinyl masks like that and they're very thin. If they were any type of plastic or plastic like material it would have to be pvc. If it was PVC, vacuum forming wouldn't leave trim like that so then the liquid would have had to have been liquid resin and not silicone to do a resin casting and would still need to be thick enough not to have any flexibility. Just with how long it takes her to punch the hair that they had to speed it up, and the mask didn't flex from its shape 1 time, even when removed, and she was very jentle with it, something you'd expect more with a thinner resin that can break vs a thick plastic, which I would assume would be just as difficult as a resin cast to punch the hair in. Not to mention the amount of multiple masks they had and would have to have each strand punched in the same spots, not easy to do unless you had, say, some small poke marks in your sculpt, which would be way easier to sculpt in, choose depth, and the place of each hole if you had a 3D sculpted as your base vs doing it by hand
Not to mention all the scratches on the mask, maybe they were sculpted into the mask and couldn't be seen because of the plain opaque color, but having added scratches to a weathered cheap Chinese resin copy, removed 3/4 of the padding and having it just on the cheeks, eye sockets, and forehead and then taking off the 5 point strap and replacing it with an elastic strap that's just secured by a strong version of gorilla glue, I can say it's not only easy to add scratches to resin if you needed to further weather it, but they're not that heavy unless they're cast really thick. And even when cast thin they don't flex, they're just fragile and can break if dropped