In this context, it usually means the installer or the specific combination of updates/DLCs is unique to that uploader's release. Best Practices for Posting
Combined, the phrase most likely refers to an ElAmigos repack or pirated release of Ghost Recon Wildlands — possibly a multiplayer-capable ("Multi") repack or a variant labeled "exclusive" by the release group. tomclancysghostreconwildlandsmultielamigos exclusive
A: If you use the mods while connected to the official servers, yes. The exclusive guide requires you to block battleye.exe via your firewall. In this context, it usually means the installer