Take the VX-64, for example.  Let's assume I prefer it's DeEsser.  Does it make sense to use it only as a DeEsser, or would a dedicated plugin like the BT DeEsser be a better choice in terms of saving computing power?  I assume the single plugin is less power hungry, but I also know some individual plugins are heavy hitters.
 
Alloy has a Transient Shaper I find easy to use (and a nice EQ), but is Alloy chewing up valuable resources whereas the TS-64 isn't?
 
Maybe I can get the answer from the performance meters.  Maybe it's a stupid question.  I just know that I avoid using a suite for a single purpose and I am questioning that.  An exception is Nectar.  Usually I only use its Harmony Module.

A bypassed module should not require CPU resources, but it still may require RAM. Also, a stand-alone effect may require more resources than a complete strip, this depends just on how either is implemented.
 
You can simply try in a otherwise empty project how much CPU an effect requires by watching the performance module in the control bar. E.g. turning on the Deesser only shows less CPU for me than turning on all effects in VX-64.

FYI the TS-64 has a lookahead function, so be aware of that.

The reason the Channel Strip-based effects use (in most cases) slightly more resources is because they are operating in a shell.  You're loading the entire CS regardless of how many components you enable.  There is a slight bump in overhead due to that alone.
 
If conserving resources is an issue, I suggest going with application specific plugins whenever possible OR committing to your mix decisions and "printing" (bouncing) the FX'd track to audio.