No bro ... you must not confuse the splitting a file into multiple files, and split a data folder in multiple folders.
The programs you use split a data folder in multiple folders, for then be compressed, in the simplest and fastest way, with the compatibility of installers created with inno-setup-script.
The second innovative method and not yet tested, is to compress the entire data folder in an archive, split the archive to the desired size.
For example in this way we will have an archive from 5GB (Data.arc) and the possibility to split the archive into 5 parts each of 1GB (Data1.arc, Data2.arc, Data3.arc, Data4.arc, Data5.arc)
This way you avoid the problem of the impossibility of dividing a data folder with inside an file of size greater of the size you set.
The whole thing is possible with a tool like this:
The idea of installation of splitted archives via installers compiled with inno, is this:
You compile the installation script with inside "dlgj+.exe".
During installation they join archives split by the start process "dlgj+.exe", creating the archive reassembled in the windows temporary directory, the installer will make its course by installing the game in the selected folder, files created in the folder temporary are deleted after installation.
Example merge split archives : Attachment 14258
If some friends here on the forum with good knowledge in programming with inno-setup script is interested in modify the installer with the start of the process (dlgj+.exe) to merge an archive split during the installation, I think the work can go forward.