You can find the download links and gameplay previews for various versions through these community sources: KOF Theory Mercenary V2 (Facebook Link):
I have included : one for a forum/readme description (detailed) and one for a YouTube video description (concise with tags). kof theory mercenary screenpack 400 slots down link
400 slots is large enough for variety but typically avoids the extreme lag or loading issues seen in "Mega" rosters with thousands of slots. Top Features You can find the download links and gameplay