This post below to another topic fixed both my Serial Issues for Particle Dev and CLI. Since I don't get an error anymore in Particle Dev, the 1.5.1 version must be the latest and greatest and I shouldn't have to install Atom 1.5.4. I'm assuming when it is updated by the Particle Team the Update Button will auto-magically take care of it, or point me to the proper procedure.
Continuing the discussion from [Particle Official] Windows 10 Full CLI and DFU Setup: