Hello Jean-Luc, welcome.
Please use the appropriate app topics, instead of starting new ones (there’s a system here). Links can be fount at the homey.app store app page. Thanks!
Also, please read the Welcome to the forum guide:
https://community.homey.app/t/welcome-to-the-forum/31
How to ask a question:
https://community.homey.app/t/tip-problems-with-homey/35744
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An app is on it’s way, so this means just to have a little patience for you 
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already requested:
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When G assistant supports both devices, in theory yes. But there can be a (big) lag up to 30s. For a sensor it is not very usable, when immediate motion event triggers are desired.
The TRV then can be driven by a virtual thermostat, as if it were a Homey device.
The presence sensor can turn a virtual sensor/switch on and off per Google Home routines, as if it were a Homey device.
Not sure what you mean. Both devices are zigbee devices, from Sonoff, not Tuya
