Here is the sad truth about the hyped Kayfun V5:
Even with the M2L Kit, which I have, it does NOT make the Kayfun V5 a good MTL device. The reason is that the V5's inner chamber is too big, which means muted flavour when you draw because you first need to suck out this air.
I have the V5, V3 (Plus) and a bunch of old KFL2+ - I am a very "extreme" MTL vaper who likes airflow very, very tight. You will laugh, the best OVERALL experience after weeks of comparing all the Kayfuns is still the KFL2+
With the exact same wattage, coil and liquid, at about 14-16W there is a flavour note/kick with the KFL2+ which is NOT there with the KF5 and possibly also not with the V3, although the V3 might come close. I tried for the longest to find out what the difference is (because I couldn't explain it) until someone mentioned the larger chamber of the V5 responsible for the muted flavour, which makes total sense to me (As said, this is WITH the M2L kit).
For M2L, the V5 is extremely overrated and overhyped. It is BY FAR not "a great M2L atty"! I also find its airflow control entirely ....ty and non-practicable and in general it's a very "meh" atty for M2L.
** Why I still like the KFL2+: As said, overall best experience for MTL, it has the "perfect" draw, it has the biggest tank capacity (4.5ml in my case). All you need to do is wick it properly (which took me months to find out

), that is, when you wick it you keep the juice channels on the side unobstructed by cotton. (With a small screwdriver etc. you push the cotton inwards towards the chimney)
I don't know about any of the other mentioned devices, but I think I'd simply get some super-cheap KFL2+ clones for $9 or so rather than any of the newer devices. All I know is that when someone says that the V5 is a "great MTL device" I have reason to not take their advice