In arcade emulation, games often share files. A "Full Non-Merged" set removes these dependencies so every ZIP file is "standalone".
If you need a curated small set, look for “MAME 2003-Plus reference full non-merged” collections (often 5–15 GB for thousands of games). mame 2003-plus reference: full non-merged romsets
Non-merged sets take up significantly more disk space because data is duplicated across ZIP files. However, for a 2003-era set, the total size is still manageable (usually under 30GB–40GB). Critical Compatibility: The 2003-Plus Samples In arcade emulation, games often share files
A merged set combines the parent game and all of its regional and bootleg clones into a single, massive ZIP file. In arcade emulation