If a site has two WaaS appliances, can one work at peak performance while the secondary takes over when needed  (e.g. if the primary reaches its connection limit) or should the connections be equal between the two appliances?

I have a wae that continues to be recognized by the CM, even though the device is inactive and has been completely removed from the network.  The device was uninstalled and removed from the CM per the Help instructions, but the device is still listed...