The game splits its massive world data into chunks to manage memory efficiently. You will rarely edit x64.rpf directly. Instead, using tools like OpenIV, you navigate inside x64.rpf to find further archives (x64a, x64b, etc.), which contain the actual game data.
: Modders rarely edit the original x64.rpf files directly to avoid game corruption. Instead, tools like OpenIV allow users to "Copy to mods folder," creating a duplicate path where changes can be safely applied. Gta 5 X64.rpf All Files