FBA Next Packs are not random folders of games. They are curated using DAT (Data) files. A DAT file acts as a blueprint; it tells the user (or the ROM management software) exactly what files are needed for a specific game to run, down to the exact byte size and checksum (CRC32, MD5, SHA1).
Finding FBA Next Pack ROMs can be a bit tricky, as they are often distributed through online communities and forums. Here are some popular sources: Fba Next Pack Roms
FBA Next represented a significant milestone in arcade emulation, focusing on speed and performance over the absolute hardware accuracy prioritized by MAME. Historical Context FBA Next Packs are not random folders of games