I have four SONOFF 4 relay to control 16 switches - combo of lights and fans. I also have individual Sonoff basics. I also got Yeelight and also cheaper Yeelight knockoffs from Aliexpress. All of them work with Alexa and Google - although for some strange reason I always have some that dont work
As for Sonoff 4 channel relay - for that matter any sonoffs - they are a pain in the back if internet is not on (unlike individual sonoffs which are mostly external - three of my Sonoff 4 channel relay are inside the wall. Last week when I forgot to renew my hathway - well during Night I switched on my bedroom light and fan using Alexa - midnight hathway disconnected internet and next day morning when I asked Alexa to switch off bedroom...she ignored me. I googled and there seems to be a LAN option and also some tasmota flashing thing for Sonoff - need to research this further to make sure it works when net is off.
So bottomline is that if you plan to insert these inside the wall and for some reason there is no power or internet....workarounds are painful. But on the flipside - I really enjoy the investment in these. Even my 75 year old mom asks Alexa or Google to turn off few things!!
While the 4 channel ones might need an electrician - my 13 year old is the expert on smart LED bulbs and Sonoff basic.
Oh yeah...apart from using voice commands...all my garden lights and also few other lights turn on and off at preset timelines...this is a really useful feature to have - particularly say for those that dont live in flats but some lights to turn on even when they are not home - kind of trying to fool would be burglars- this was the main reason why I installed my first 4 channel relay
Next project is to use IR to tell Alexa to switch on and switch off and also change channels on tata sky. I dont want to use harmony hubs or IR on mobile phones - Please do let me know if you have done anything in this regard
Below is an old video of my kids showing off bits of home automation way back in 2017!