CPU Usage - When and when not?

A couple of basic questions if I may:
 
Do soft-synths and associated tracks that have been bounced to audio and then muted still use CPU? Does archiving them or freezing them reduce any CPU Usage?
 
If an Effect is assigned to a track or Bus but is bypassed does it still use CPU or only when enabled and processing?
 
Do Midi\Softsynth tracks use more or less CPU then the bounced audio track? Meaning is it best to wait to bounce them until ready for the final mixdown to reduce the amount of CPU being utilized?
 
I am just trying to understand this a little better as I have pushed the limit a few times (with an I7, 10000rpm digtal radon drive, 8gb memory)? I can obviously shut down some other services that are running or even set up a different profile that is barebones which I may do anyway. But want to use Sonar the most efficient as well.
 
Thanks,
 
Joe..