Almost any regulated mod would be a good choice.
Kayfuns get a little touchie over 20w, keep your coil builds between 1.3 & 1.8 ohms I find 1.6, 1.7 ohms at 17-18 watts 5ish volts to be my sweet spot.
No doubt the 3.1 IMO is the best kayfun version,and I love the heck out of all my kayfuns, but if you really want to expirence an awesome vape at any setting you throw at it, get your hands on an Eleaf Lemo.