in fact if you install the ftdi driver it will not work and you will be unable to upload sketches to you arduino.
Yes you can just turn it of whatever you want.
Well to be a little more clear, one may need to have both Uno or mega2650 drivers AND ftdi driver if they own both older and newer types of boards and plan on using both of them either at the same time for individually at different times.
Some of us just could not handle owning just one type of Arduino board. ;D
Lefty