Definitely some good advice, I don't know if this has been said before but with vaping and especially the style of tank you are using that doesn't have much airflow(air intake) mouth to lung inhales seem better. I work at a B&M vape shop and alot of first timers have this problem with harshness and choking, telling them to do mouth to lung has helped alot. Also Nic content and pg to vg ratio (VG is smoother, less throat hit) certain flavorings( I find sour citrus flavors to be harsh) all play a role in the throat hit.
good luck