[ubuntu] Do I need to install Graphics and sound drivers on ubuntu 16.04?

Answer is maybe.
Depends on hardware.
More likely a probable for graphics than for sound.
It's very rare you would need sound drivers beyond those already installed.

But if the system works out of the box then you probably don'y need to do anything about drivers.
Linux has builtin drivers that support a wide variety of hardware.

But if you feel performance lacks then you might look into Ubuntu driver section in the program Software and Updates >> Additional Drivers.
If there are any known drivers that are not part of the default install available for your current hardware using your current system.
They will be listed and installable from here.