Every cpanel server should be need to optimize according to your server usages, I hope the following articles will help to improve your cpanel server performance.
Run your cron jobs at off peak hours.
Go to WHM > Server Configuration > Tweak Settings > Disable Spamd
Go to WHM > Service Manager > Disable Spamd
Disable Anonymous FTP
Go to Service Configuration =>> FTP Configuration
If you or none of your customers aren’t running any mail listings through cPanel, it would be a good idea to disable Mailman.
Go to WHM > Server Configuration > Tweak Settings > Disable Mailman
Catch all can use up many resources and storage space, To disable CatchAll
Go to WHM > Server Configuration > Tweak Settings > Change to :fail:
Tweak Apache to reduce lot of memory.
Change the following settings depending on your server usages.
Save and restart apache now.
Install PHP accelerator (Recompile Apache with eAccelerator)
Compiling Apache with mod_deflate Gzip Module
Turn Off unwanted statistis
Analog Stats, etc.,