I am currently happy with Home Assistant Operating System running on a RasPi 3B, with 3 TP-Link energy monitored power points and 3 LIFX light bulbs. I am renting, so don’t imagine adding many more devices.
I have however realised that controlling HA from a smartphone or even a dedicated tablet will be less than ideal; the Goodle/Alexa demo received good WAF
Rhasspy seems to a better approach for voice control, and I am awaiting a ReSpeaker 4 Mic Array for Raspberry Pi.
I note that Rhasspy can be installed as a Hass.io add-on; or on its own RasPi 2, 3 or 4. So, I am wondering whether it would be better to install Home Assistant, Rhasspy and Node Red all on my Raspberry Pi 4 4GB (thinking inter-process communication will be faster than between machines), or would I be better off splitting the functionality between Raspberry Pis (effectively providing more concurrent processing threads) ?