How are you?

I would like to ask about Monitoring Servers using Agents under Monitoring in admin page, 

What information i will get from using this agents?

 And what if i plan to not using it and just use SNMP or WMI credential, do i loss many data from servers?

Is there any traffic or loading on CPU & RAM when using Agents in servers?

Can i monitoring my servers only using Agents without using WMI & SNMP credential ?

thanks