Hi, english is not my native language so sorry if I mention things youve already talk about in you post.
I've actually found 3 things in particular:

First I search an object, because I found those sort of marks on a room in the map and on an another secret room (maybe the one about the caesar ciphers that you talk about.
I've finally found it and it was located right here for those who wants:
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2701365902
It was in the sort of "pool hole", its behind a fake wall

Then I've put the object in the square with a strange form on it and here's what appared:
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2701365659

https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2701365528

https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2701365775

I dont know myself in enigma, I've try to search the word that appeare on one of those enigma: "daecraogrittt" but it gave me no result at all. But I think each one of those enigma give a letter, wich then is supposed to make word, and I think this word is useful for this secret hidden room:

https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2701366033

But it can be a caesar code as you said tho

That's all I found, I'm on my way to try to maybe find more things on this map

If you find anything too, feel free to respond, and if you know you yourself in enigma pls respond too (I'm talking to anyone who see this post)

Btw, I'm gonna try to scan it to watch if its a QR code, I dont think it will work, maybe we need like to take a pic of the map from the top and put the colors in black and white a software like photoshop or something like that

Alright I tried to scan it like a qr code but it didnt work, maybe need to reverse the color or something like that but idk how to do that, I'll still try to do it

Okay so I may have resolved two of the enigma, those ones:
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2701365659

The one on the left make the number four, because there is four squares, and the one right make the number five, because its roman numeral and it goes from 1 to 4 and next, logicly, its five.

The answers give letters, like I was expecting, so it may resolve the secret room problem, dont know how tho

https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2701366033

I asked on reddit if anyone could help, still waiting for a response, I'm going to try reverse image search those two ones that I cant solve while waiting, hope I'll find anything

I found a missing decal - https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2703338911

._.

i think i know the answer for the room

i think the room were you put the stone in it spells FORIN

Well, i found a capybara hidden behind a fake wall https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2703807227

but i might be wrong

FORIN? Humm it can be correct but for me there where at least two f in the answer, because of the previous enigma wich gave me four and five, how did you found FORIN?

btw Aztekgp how did you found the capybara? I took hours and hours trying searching others secrets on the map lmao

I was no-cliping around and i found a room with a yellowish light, when i approached it had nothing in the frame, but, when i exited the room and entered again, the capybara was there lol

ho yep, I just found it lol, lil capybara, interesting but I dont think it has anything to do with the global enigma, sh*t, darn this enigma is really hard lmao ;-;

Don't know what it means but it might help
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2704035091

Also above the capybara.
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2704041488