You probably won't ever see definitive reviews: It looks like one of those models that could be several different chips that OEMs can brand as a 940mx. It could be like an overclocked 730 or a 750m or something else-possibly even an old Kepler part. Performance of these will vary widely from one laptop to another.
If you want to know what you are getting for a laptop GPU, you need at least a 950m-something for which they actually list the specifications.