So a plugin that detects that a player is using a minimap mod? This won’t be possible because there’s nothing a server can for sure detect. Although the forge client sends a list of installed mods to the server, this isn’t safe. Another forge mod could simply change that outgoing list and therefore make the minimap mod invisible for the server.
If you want to prevent that the player can see many chunks around them, you would have to reduce the view distance in the server properties.
To make using xray difficult try this plugin.