Hello!
i am woundering how can i check people if gameban / Vac ban / Server ban on a new account?
any website i can check with steam id? or plugin to use? or anything?

Game/vac bans are linked to players steam id. If a player has multiple game and vac bans and creates a new account that is exactly what it is, a new account and the bans won't show.

for auto checking and kicking for bans  try

https://umod.org/plugins/server-armour

I still use Steam Checks plugin and RustAdmin,  RustAdmin has the advantage of showing isp which makes it easier to check if suspicious of like behaviour.

thanks for the tips nash / pook :D