Webflow manager client usage and how to verify the installation

According to Install and configure workflow for SharePoint Server, each server in the SharePoint Server farm must have the Workflow Manager Client installed. I can easily verify Workflow manager is installed on SP2016 App server (with Get-wffarm).

My first question is how to verify “Webflow Manager client” are installed on all other servers beside checking “installed program” and “web platform installer”? I am not comfortable for the indirect checking methods. Can I run some command or query a web service URL to verify?

My second question is what is the usage of client? I cannot find any article discuss the usage. I tested our SP2013 workflows are running fine even I am sure it is not yet installed on Search server.