client mods wont jack your performance either if you're hosting from a dedi. the only mods that will mess with your server performance if you're hosting through a dedi (which you should be if you're doing a serious server and your normal bl lags while playing usually) are ones that run schedule loops, like Event_onGaze or the such, and even then its minimal impact.
the reason you shouldn't be hosting with a client (game instance, whatever) if playing bl normally lags is because when hosting, the server is directly tied into your game instance, so if your game lags, so does the server.