I had this question after viewing
Z-wave v ziggbee v LightwaveRF.
Can someone please confirm that my understanding of zwave plus is incorrect? I assumed that if I had 10 devices that were zwave plus and if I then added a standard old zwave device (not the new zwave plus), that the whole zwave plus network defaults to a standard zwave speed or it is just along that one non zwave plus path that gets effected i.e. slower?
The whole ZWnet speed, if there are mixed ZW (old and new gen), will be the speed of ZW (old) not ZW (new gen). Some that is very particular about speed may run independent ZWnet. But note that in ZW mixed environment, there can still be greater ranges, update of firmware and less power consumption to strive for its existence but the deficit to stay with such deployment is in attaining higher speed.
Henceforth, as part of the planning to upgrade from mix environment or to even start first before deciding to go for "mixing" is to minimally have the first element in your ZWnet, which is the ZW controller to move into an new Gen (ZW+ support) so as to take advantage of the higher speed in all your net, or part of it if you still decided for the "mixing" i.e. use any old ZW device.
reference - https://www.domoticz.com/forum/viewtopic.php?t=9618