There are some different versions. I am using clones (Ehpro) of the Kayfun Lite Plus V2. The V2 (clones or authentic) are the latest version of the Kayfun Lite. They are 22mm in diameter so they are the same diameter as a standard mechanical mod. The Kayfun mini is a smaller diameter atomizer, which I have no experience with.
There is also the original Kayfun 3.1, which is the first. The Lite version is...obviously...surprise...lighter. It also has some other improvements over the 3.1. Unfortunately I have never owned one and don't know for sure what exactly the other differences are.
That's really all I know about the previos versions, maybe someone else can help, though I am VERY pleased with the V2 and therefor have no reason to research the older models.
And yes, the authentic Kayfun is made by Svoë Mesto.