Of course, thank you so much for responding.
So this is my wiped Mod folder, very standard, I don't have anything in it right now, and then there's how it typically looks when I have folders in it (I wasn't very far into redownloading when the game started crashing) And I'll add the inside of one of my folders as well. I don't use sub-folders obviously, but just for the sake of clarity.
The crashing started after I added the Aira-CC stuff, which had never caused a problem in my game before. I took the folder back out immediately but the game continued to crash on launch. I wiped my Sims 4 folder and only reloaded my Saves and that was fine, but as soon as I started adding the mods back in, I had the same crash issue, no matter what file or folder it was.
Better Exceptions flagged one of LittleMsSam's package mods yesterday, which I removed, and it hadn't caused any in-game issues.
All files and all folders were working absolutely fine in-game before I added the Aira-CC ones. Between downloading them and adding them to my Mods folder, I did connect to the Gallery in my game for the first time in months, though I doubt that's relevant, but just to give all the info I can.
Thanks so much again