The best Temperature sensors are Hue Motion Sensors, (£29) I am using ~30 of them for many years, they are rock solid on a Hue hub. They have the added advantage of running 2 years on two AAA or AA for external variant. Also the battery reporting very accurate and you can run them down to 20% and know you still have a good few couple to get around to changing batteries. Plus of course it has Motion and Luminance. These are the best bang for your buck if you are using zigbee.
They were not so good on the HE Hub until I added 4 Ikea zigbee Relays (£8 ea) and now they are great.
I have been using Secure Zwave SRT321 (known by multiple different names), for a few years, they are thermostats but report temperature accurately like clockwork every 5 or 15 mins. They can chew through batteries so converted 10 of them to use battery eliminators
I have been testing the Sonoffs for last 5 months and found that I get a disturbing amount of failures , that makes them unsuitable for heating systems, from them where instead of reporting every 15 mins they can go hours or days without reporting. I have had two fail on install because they were poorly assembled and the pairing pin was not properly seated so when you. press the Pair button the micro switch beds and breaks off the circuit board. They are cheap and if reliability and build quality is not an issue then fun to play with.
I have been testing two other Temp sensors for the last month or so that are looking very promising.
Aeotec AerQ - which I have set to report when Temp changes by .5C and that is doing very well indeed. They brought a built in driver for it in 2.26 but it is not quite there yet. and lacks that standard offset delivered for other built in drivers.
Tuya Temp/Humidity Sensor - which also just reports on change and appears to be very economical with batteries. So far have been showing a lot of promise.
Because I run multi zone heating I like to have multiple temp sensors per room and I try to have one zwave and one zigbee per room so they can audit each other and gives me a degree of redundancy.