Hello! I understand that in vanilla you can not put plugins that affect visually, but internally it is possible? I want to use plugins like steamchecks to avoid people with VAC. Will my server receive any sanctions for this?

Hi,

Yes you can put this plugin on your server, administration tool is allowed ;)

Every plugin that didnt change VISUAL / GAME MECHANIC to players is allowed (you can use admin things like Admin radar, etc)

Facepunch allows admin tools only.