I've installed all three 64-bit versions with the @wal24 skin, but only one folder named "voice/" under iGO_World. In the other two versions, I reference this folder (Content/) in the SYS.txt file.
So I can access this single voice folder from all NG versions – however, my Samsung S21 is having problems with the TTS voices, so I'm only using the old *-lua.zip files. 👍