Question
Does installing Workflow Manager, 2013 workflow platform to my farm benefit Nintex?
Answer
No.
Nintex uses the 2010 workflow platform on SharePoint 2007 - 2019. Enabling Workflow Manager will not provide any benefits to Nintex Workflow.
Nintex uses the 2010 workflow platform on SharePoint 2007 - 2019. Enabling Workflow Manager will not provide any benefits to Nintex Workflow.
Additional Information
There are many reason why Nintex stayed with the 2010 workflow engine. One reason is the ease of migration. Workflows created with Nintex for SharePoint 2010 can easily be migrated to SharePoint 2013 and so on up to 2019 as the workflow engine is the same with all versions.