Couple of questions related to Tado products

Current setup

I have a combi boiler plus 3 heating zones controlled by separate 2-port zone valves. One is wired controlling a one-zone wet underfloor with it's own timer, one it wireless, again with it's own timer and receiver wired to the boiler and one is wired to a separate controller/timer.

1 - Seeking confirmation that just replacing the TRV heads with Tado Smart Radiator controllers won't in itself do anything as there is nothing within that setup to switch the boiler on or off. 

2 - For now I am inclined to leave the underfloor thermostat/timer alone in which case I would need to replace either the wired or wireless thermostat if I want the radiator controllers as well.

Is that correct ? The diagrams on the Tado website indicate that the radiator controllers "communicate" with the internet bridge which then communicates a call for heat via the wired/wireless thermostat (regardless of whether the stat itself is calling for heat or not).

I guess another option would be not to replace the existing thermostats but just leave them permanently "on" and rely on the Tado devices. Is this what they refer to as "bridging" ? 

If this is the case then it seems a bit lacking as once I am able to control the temperature of the radiators then why would I need a separate wall or room stat ?

Lastly, I have a three story house so presumably the placement of the internet bridge is important because it needs to be equidistant as possible to each of the radiator controllers but at the same time it needs to be wired to the router.