Hi monofase,
Temperature is not linked in any way to the link width nor the protocol. Generally speaking Samsung drives run hot (my 2TB 960 Pro runs at 55°C idle and 73°C after huge transfers), but Kingston / Toshiba drives, even being fast NVMe drives with 4x PCIe 3.0 lanes, run at 39°C idle and 58°C after a long blackmagic test.
Very interesting. On Win10 1709, 2015 MBA 13 my 250GB 960 EVO runs extremely cool; it idles at 40C and rises up to 50C when I stress it with CrystalDiskMark 2GB. Could you please download CoconutBattery and tell us the power draw when doing various tasks with the Kingston/Toshiba drives (the figure below) and the MacBook model? I get 8-9W in HS 10.13.4 normally.
I successfully upgraded my 2015 15" rMBP with a large black Sintech adapter (ordered from Amazon US) and a Toshiba XG4!
I am currently doing a battery life test as well as compared to the stock SSD and I will post that as well later.
I eagerly await uintmax's battery life test with the XG4. I have seen tutorials on YouTube where people claim that there is no noticeable battery life drain with SM951 and rMBP because as stated above in this thread it's most similar to Apple's native UBX SSDs. 960 EVOs and 600p s are known to have higher than usual power draw based on experiences in this thread (I remember Audit13 mentioning this earlier.) If it really turned out to be the case that some SSDs have lower draw than others we should create a guide for people who need the extra battery life.