Definitely Zigbee or Z-wave instead of wifi. Once you start to build out more devices you will be glad to not have gone down the wifi route.

I went with Zigbee and have Sonoff SNZB-02 temperature and humidity sensors in each room that have been absolutely flawless since the day I installed them, and they last about two years on a single battery!

I would obviously recommend them but I don’t have any experience of other thermostats or of Z-wave.

I did also install smart Zigbee TRVs on each radiator but I don’t rely on the internal thermostats of them as they don’t accurately represents the overall room temperature.

In the UK I’m paying £53/months for 1Gbps fiber