Here is what I can't figure out. I used to smoke (deep inhale) hookah tobacco (smoke not vapor) that is loaded with nicotine. I'm vaping at about 30 watts .35 ohm with 3mg of nicotine, and I'm coughing my head off. Puzzled??
You mention you vaped a few years ago, was this with more restrictive airflow?
You may find if you have just started vaping again, a really airy, direct to lung draw is not for you, and a mouth to lung tank might be better, with higher nicotine juice to start with, or you will experience this coughing.
Also, as mentioned, with a regulated device you can put the wattage wherever you want, your resistance doesn't matter in regards to amp load on your batteries, watts do, and at 30W you are drawing at a maximum just 4.68A before chip efficiency-once this comes into play somewhere around 5.2A is likely.
This is assuming you are using a series, dual 18650 device, as you mention it is a 150W mod.
You could try turning the watts down a little bit to see if this helps you with the coughing, but it is likely a MTL setup will be best to start with.
EDIT: I should add, I am calculating with a cutoff of 6.4V-if the mod cuts of at 6.2V it will be slightly higher, but still well within safe limits of a 30A cell, which you mention you have-but unless they are something like LG HB6's they are likely 20A cells, but still more than enough for your needs

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