There’s a folder called “StreamedPackages” in here:
AppData\Local\Packages\Microsoft.Limitless_8wekyb3d8bbwe\LocalState\StreamedPackages
(MS Store version)
This seems to have all the aircraft, airports, challenges etc in it - currently this is sitting at 5.7 Gb for me. Note that this is a symbolic linked folder -so actually is stored somewhere else - I assume in the folder where you actually installed MSFS 2024.
There is also the rolling cache, which is 16 Gb by default and (also be defualt) is in this folder:
AppData\Local\Packages\Microsoft.Limitless_8wekyb3d8bbwe\LocalCache
again, MS store version
I believe the streamed world data is stored here, as and when you fly. Again, this is a symbolic linked folder so doesn’t actually live in your appdata folder (typically on your C drive).