I install Nintex Workflow 18.104.22.168 on our farm, and tick off to include "Live". We've had a previous version of Nintex Workflow (22.214.171.124 I think?) installed where Live wasn't included.
The result: Nintex WF is upgraded to 126.96.36.199 and the installation finishes witout errors.
What I can see is:
Entering "Nintex Live Management" in Central Administration produces the following error: 'LiveAdmin_Page_Management_Title'
Tracing this in the ULS produces the following:
Failed to open the file 'C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\15\Resources\ninlivadm.en-US.resx'.
Failed to open the file 'C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\15\Resources\ninlivadm.resx'.
Those files doesn't exist in the 15 hive, although the rest of the Live installation files have been put there (ninlivecore.*).
Retract/deployment of nintexlivecore.wsp
Reinstall of Nintex Workflow 2013.