I have 3 Kontakt 5.whatever   appearing in my default VST menu
 
they each appear identical...
 
!) why? (do I have three?)
2) Does it matter which one I use?
3) If I create my own VST menu, which one do I choose (again, does it matter?)
4) If i use the default menu, (I've not had good success in creating custom my own custom menu) which one to select? 
 
Thanks! 

Each has a certain number of outputs. 8, 16 and 32 I believe. 

You can identify which is which by checking, in
"Soft Synth Options" the "all synth audio outputs - stereo" option, and then inserting the synth.   This is done from the Synth Tab in the Browser; I don't believe you can get to these options under the main menu "Insert - Soft Synth- VST2" .  
 
On my system, they are in odd order from the top:  smallest (4 stereo output tracks) then largest (32 stereo output tracks) then medium (8 stereo output tracks).   And that never changes, so if you decide which you like, you'll know by the order.   
 
Edit -- oddly, it is 16 stereo output tracks, or 32 mono tracks, but for some reason Sonar inserts 32 tracks for the largest version and 8 for the medium version.     Probably just another bug.

You can also rename these in Plugin Manager with a double click on the 'Kontakt' name. 'Kontakt 'x' Output', 'Kontakt 'xx' Output', where 'x' = the number of outputs. This naming will display in the browser.

Thanks BillWatkins!    You do have to close and then re-open Sonar to see the name change, I believe.

John
Each has a certain number of outputs. 8, 16 and 32 I believe. 

OK, I've been confused on these exact #s... I think the above is correct if you're using it as "mono" outputs (assigned within the 16 midi channel framework)... 4, 8 & 16 if stereo...even though it'll still have unusable Left, Right, stereo listings in the pull down in the audio tracks pull down input assign thingy on the "audio" portion of the audio/midi tracks.  If you have the "32" version up, it'll say "out of outputs" or some such after you assign 16 stereo instruments... it is a bit confusing when you mix the two, for example, if you have several "mono" sounds on the same channel you can exceed 16 tracks but if using some stereos, as at some point you'll run out of outputs... 
 
did I manage to make sense with the above?  am I confusing something beyond the confused issue postulated above? I ask as that is how I've interpreted what is happening when I try and add beyond sixteen stereo tracks (as 32 mono LorR/stereo are listed).  I'm curious if I've misinterpreted what is happening. 
 
At any rate, as I seem to always use "stereo" outputs I labled mine 4, 8, & 16/
 

The Kontakt manual suggests that using different versions of the VST (different number of outputs) in the same project "...can seriously confuse your host and lead to unexpected behavior..."    

williamcopper
The Kontakt manual suggests that using different versions of the VST (different number of outputs) in the same project "...can seriously confuse your host and lead to unexpected behavior..."    

Furthermore, I read that there is no CPU savings using the smaller one. It is only there for compatibility with certain DAWs that can't handle that many outputs.

I have "VSTPlugInNameFormat" (option) and "0" (value) set in Preferences->File->Initialization Files, so I can easily distinguish which one is which in the Browser.
 

 

 

I generally use the large one...have an empty template set up and several setups, like an orange tree guitar set up template. I just delete unused tracks and use the batch safe feature ( I'm mobile at the moment).

The large 16 outputs WILL use more memory/cpu if you use more instruments. I generally use 4 to 8 per instance to spread the load among my 6 cores using multiple kontakt instances