The main issue with concentrates are residues, I noticed I never cough when I take a low-temp dab (540 on my e-nail) on a CLEAN nail, if I take several dabs on the same nail without cleaning, they are harsher and harsher and I have terrrific cough!
So after each dab I make a small coton ball and clean my nail to new before the next dab, using this method every dab is sweet and smooth.
The problem is the same with wax pen, too much residues and coughing occurs but t°, wax quality and attys components are the key also. For example i own a Divine tribe ceramic double coil atty....it makes me cough at hell...as i would to put my lungs out! and in another hand my old kiss cart 7.4v is smooth as my dabstorm or evolve. I have nothing against DT, I loved my donut V1 but i hate the double coil atty they offer for the coughing reason!
I can cough using flowers also...especially using a good convection device and a large load at high t°!
Conduction doesn't irritate my lungs as much as convection...sometimes I'm stocked to see I can manage some milk style hits without any cough (with a true conduction unit) and in another hand some whispy full terpènes hits are difficult to handle for my lungs!