It is possible both ways (didn’t know that yet, found out while fiddling with it )
Without a flow needed, I coupled my Tado thermostat with a VThermo.
Open the settings of your VThermo, and look for Target temperature in the same zone
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Ticking the upper box sends the target temperature from other (hardware) thermostat(s), to VThermo in the same zone.
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Ticking both boxes sends the target temperature to other (hardware) thermostat(s) in the same zone, and vice versa. They both follow eachother.
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Ticking the lower box only sends the VThermo target temperature to other (not VThermos) hardware thermostat(s) in the same zone.
Functionality showed here: https://youtu.be/gV9X9aMx8b0
Hope this is what you were looking for.