Do you remember when you installed the Horizon Agent, which features you included? even months later? The install is so easy that we tend to forget all the options we configured and then someday your testing is not going to plan and you learn that you needed to install a component during the agent install. Well not a problem! You can actually view all the installed Horizon Agent components right from the registry! Just open your registry editor and browse to the following path: HKEY_LOCAL_MACHINE\SOFTWARE\VMware, Inc.\Installer\Features_HorizonAgent
Can I turn features on and off using regisrty?
no. Uninstall and reinstall agent is the best way. You can also try modifying using Add/Remove Programs, but not recommended (by me).