No, there haven't been any reports of the Vivo Z1x having any heating issue.
So, it can be concluded that it doesn't have this issue.
Check Full Device Specifications Vivo Z1x
Normal mode and Night mode. The 32MP selfie camera of the Vivo Z1X is also very capable.The selfies shot this phone to be sharp with good amount of details and colours.Night mode is available both , Front and Primary cameras.
In the meantime,do not forget to find all the detailed specifications and other latest updates about the device here.