The undershoot is more of a personal preference. I prefer never exceeding the set temperature, even if that means lagging a bit when I draw too hard. Reminds me a bit how conduction vapes work... without the downsides of course.
But ideally we would want the live temperature to be exactly the set one and stay solid of course. It's just that I never really managed to get it perfect on my joyetech cheapos. Indeed other better mods don't require that much geekery... and to be honest it's better this way!
With myevic try adding some D term, like 5 or 10 to begin with. You should be able to setup P to have a fast ramp to set point, I to prevent overshoot and accelerate the stabilization around set point, all of that tuned without drawing. Then tuning the D term should allow you to make the system resilient to disturbances (i.e. you drawing on the vape)
If you get oscillations, some of the coefs are likely too high. Good luck!
