You can mix and match, we have a number of BG Smart sockets, some plug in adaptors from various sources that use e-familycloud software and Hive for the heating. Hive has its own hub the others do not, the unifying factor is Alexa everything can be controlled from three echo dots in various rooms. As yet we do not have control of the oven, washer or dishwasher and somehow I cannot see us going for that as it will require quite some investment. To me it seems the choice is more between the top level controls such as Alexa, Google Assistant or Siri etc. at the moment it seems Alexa has more compatible devices. I cannot say that using Alexa is the best but market share often out trumps quality (remember VHS).

Richard