You are correct. I have an Atom sitting in a drawer from the beta test. I device can either be paired with the Vera Plus or the Atom, but not both. If you have a Vera Plus you won’t find any use for the Atom. I didn’t spend much time playing with the Atom as the Atom wasn’t compatible with Google Home and having an Atom linked to the account would cause Google Home to no longer work on my Vera Plus. I put it in the drawer at that point as the Atom seemed to serve no purpose that I could see. I would have assumed that would have been fixed by now, except that yesterday an announcement was made saying Atom now works with Alexa. Since Vera had Alexa long before it had Google, and since I haven’t heard anything announced about Google, I’d assume that still doesn’t work.
The Atom really isn’t a hub, think of it more as a bridge between a z-wave (and possibily Zigbee - I don’t remember for sure if it had that or not) mesh and a wifi connection to connect to the internet. Nothing runs on the Atom, it’s all cloud based. It has much more in common with simple, cheap wifi plugs, etc. connected via a company’s cloud based app than it does to your Vera Plus. Honestly except for the longer battery life for things like locks and door sensors, the Atom offers no advantages over say TP-Link’s Kasa line, or something similar. With either that line or the Atom you’re setting up very basic scenes through an app and relying on their servers (and you’re internet connection being up and working) for anything to happen.