The default settings are the best balance of speed and protection and if your wanting to go the free route with avast free i would suggest online armor free which includes a hips and is extreemly simple to setup http://www.online-armor.com/downloads.php and malwarebytes free http://www.malwarebytes.org/.
Ccleaner should be fine for your registry and file cleaning, any deeper than ccleaner and you run the risk of messing up your system.
You dont say what your operating system is ?